Although biological conservation has traditionally focused on the protection of pristine areas, it is becoming increasingly evident that efforts should also be made toward the maintenance of biological diversity in human-managed ecosystems. We evaluated the potential role of scattered, remnant trees in enhancing ant diversity in agricultural lands within a biodiversity hotspot, namely the Cerrado savannas of central Brazil. Ant collections were performed in, beneath, and away from the crowns of a native tree species growing in planted pastures, soy fields, and in small (<400 ha) savanna reserves. Significantly more ant species were found beneath than 30 m away from scattered trees. The magnitude of this effect was similar in soy fields and in pastures at all scales of our analyses, except at the landscape scale where the effect was comparatively greater in soy fields. Most of the species that occurred more frequently beneath than away from trees nest on ground, indicating that the conservation value of scattered trees goes beyond the mere protection of arboreal ant species. Soy plantations presented a particular species-poor ground-dwelling fauna when compared with savannas, whereas differences in the number and composition of arboreal species were less marked. In contrast, the diversity of arboreal- and ground-dwelling ants recorded in and beneath pasture trees was nearly as high as the one found in savannas. It is suggested that pasture trees can have an important value for ant conservation off reserves, particularly in regions where most of the native vegetation has already been cleared.

Embora a biologia da conservação tradicionalmente busque a criação e proteção de áreas intocadas, está se tornando cada vez mais evidente que esforços devem também ser feitos para a manutenção da diversidade biológica em ecossistemas manejados pelo homem. Nós avaliamos o papel da presença de árvores isoladas como forma de aumentar a diversidade de formigas em áreas agrícolas na região dos Cerrados do Brasil Central. A coleta de formigas foi realizada na copa, abaixo da copa e longe da copa de uma espécie de árvore nativa situada em pastagens, em campos de soja, ou em pequenas (<400 ha) reservas de cerrado. Um número significativamente maior de espécies de formigas foi encontrado abaixo do que a 30 m de distância da copa das árvores isoladas. A magnitude deste efeito foi parecida nas pastagens e nos campos de soja para todas as escalas de nossas análises, exceto a escala de paisagem onde o efeito foi comparativamente maior nos campos de soja. A maioria das espécies que ocorreu em maior frequência abaixo das árvores nidifica no solo, o que indica que o valor de conservação das árvores isoladas vai além da mera proteção das espécies de formigas arborícolas. Os campos de soja apresentaram uma fauna de formigas de solo muito pobre em espécies quando comparadas a vegetação das reservas, enquanto as diferenças na fauna arbórea foram menos marcadas. Em contraste, a diversidade de formigas arbóreas e de solo registradas na copa e abaixo da copa de árvores isoladas em pastagens foi quase tão alta quanto aquela observada nas reservas. Sugere-se que as árvores isoladas em pastagens podem ter um importante valor para a conservação de formigas fora de reservas formais, particularmente em regiões onde a maior parte da vegetação nativa já tenha sido destruída.

A gap remains in our understanding of how host-specific fungal pathogens impact negative density dependence (NDD). Here, we investigated survival of Cinnamomum subavenium Miq. seedlings, the dominant canopy species in a seasonal tropical evergreen forest, Thailand. It is infected by a host-specific fungus that is easily identifiable in the field. We quantified the effects of conspecific seedling and adult density on fungal infection and seedling survival over a wide range of environmental heterogeneity in elevation, understory vegetation and presence of forest gaps. Generalized linear mixed models (GLMMs) for seedling survival revealed that fungal infection significantly reduced survival and had the strongest effect on seedling survival as compared with conspecific density and environmental heterogeneity. Adult conspecific density was not, however, significantly correlated with the probability of infection, and conspecific seedling density was positively associated with increased infection only at high elevations. In contrast to infection, we found a significant positive correlation between conspecific seedling density and the probability of seedling survival. Consequently, our results demonstrate that fungal infection can have major impacts on seedling survival, but not in a manner consistent with local NDD effects on seedlings, as assumed in the Janzen–Connell hypothesis. Our study provides an example of how quantifying the interaction between environmental heterogeneity and a host-specific plant-pathogen can yield unexpected insights into the dynamics of seedling populations. The combined effects of host-specific pathogens and environmental heterogeneity on survival of dominant seedling species may ultimately provide a chance for rarer species to recruit.

เนื่องด้วยยังมีช่องว่างของความเข้าใจว่า ราก่อโรคที่จำเพาะกับเจ้าบ้านส่งผลอย่างไรต่อการขึ้นกับความหนาแน่นในเชิงลบ ในที่นี้เราจึงตรวจสอบการอยู่รอดของต้นกล้า Cinnamomum subavenium Miq. ซึ่งเป็นพันธุ์ไม้เรือนยอดชนิดเด่นชนิดหนึ่งในป่าเขียวเสมอที่มีฤดูกาลของประเทศไทย (ป่าดิบแล้ง) อันมีเชื้อราที่ขึ้นจำเพาะกับเจ้าบ้านเติบโตบนต้นกล้าของพรรณไม้ชนิดนี้ และเป็นชนิดที่สามารถจำแนกได้ง่ายในภาคสนาม เราวัดปริมาณผลของความหนาแน่นของต้นกล้าและต้นใหญ่ชนิดพันธุ์เดียวกันที่มีต่อการติดเชื้อราก่อโรคและการอยู่รอดของต้นกล้าในช่วงของความแตกต่างเชิงพื้นที่ในด้าน ระดับความสูงจากระดับน้ำทะเล พืชพรรณปกคลุมชั้นล่างของป่า และการเกิดช่องว่างในป่า การวิเคราะห์ด้วยโมเดลเชิงเส้นโดยนัยทั่วไปแบบผสม (Generalized linear mixed models) สำหรับการอยู่รอดของกล้าไม้เผยให้เห็นถึง ความสัมพันธ์กับความหนาแน่นของชนิดพันธุ์เดียวกัน และความแตกต่างเชิงพื้นที่ การติดเชื้อราลดโอกาสการอยู่รอด เมื่อเปรียบเทียบกับความหนาแน่นชนิดพันธ์เดียวกันและความแตกต่างเชิงพื้นที่ ส่งอย่างมากต่อการอยู่รอดของกล้าไม้ อย่างไรก็ตามผลของโมเดลเชิงเส้นโดยนัยทั่วไปแบบผสมสำหรับการติดเชื้อราแสดงให้เห็นว่า ความหนาแน่นของต้นไม้ใหญ่ชนิดพันธุ์เดียวกันไม่มีผลอย่างมีนัยสำคัญต่อโอกาสการติดเชื้อรา และความแน่นของต้นกล้าชนิดพันธุ์เดียวกันส่งผลต่อการติดเชื้อราในเชิงบวก ในบริเวณเขตความสูงจากระดับน้ำทะเลมีค่ามาก อย่างไรก็ตามการอยู่รอดของต้นกล้าสัมพันธ์สัมพันธ์ในเชิงบวกกับความหนาแน่นด้วยกลไกที่ยังไม่สามารถทราบได้ ผลจากงานวิจัยนี้ของพวกเราแสดงให้เห็นว่า การติดเชื้อราสามารถมีผลอย่างมากต่อการอยู่รอดของต้นกล้า แต่ไม่เป็นในแนวทางที่สอดคล้องกับผลของการขึ้นกับความหนาแน่นของประชากรในเชิงลบ ตามสมมติฐานของแจนเซนและคอนแนล การศึกษาของเราเป็นตัวอย่างอันหนึ่งของการวัดปริมาณปฏิสัมพันธ์ระหว่างพืชและโรคที่จำเพาะและความแตกต่างเชิงพื้น ที่ให้ผลลัพธ์ในเชิงลึก อันไม่เป็นไปตามสิ่งที่คาดหวังมาก่อนต่อพลวัตของประชากรต้นกล้าไม้ชนิดเด่น ซึ่งอาจจะเป็นโอกาสให้ประชากรชนิดพันธุ์อื่นที่มีจำนวนน้อยฟื้นตัวขึ้นมาได้.

Mismatches in nutrient composition (e.g., protein, carbohydrates, lipids, etc.) between consumers and the resources they depend on can have ecological consequences, affecting traits from individual behavior to community structure. In many terrestrial ecosystems, ants depend on plant and insect mutualist partners for carbohydrate-rich rewards that are nutritionally unbalanced (especially in protein) relative to colony needs. Despite imbalances, many carbohydrate-feeding ant mutualists dominate communities—both competitively and numerically—raising the question of whether excess carbohydrates ‘fuel’ colony acquisition of limiting resources and growth. In a 10-month field study, we manipulated carbohydrate access for the obligate plant-ant Crematogaster nigriceps to test whether carbohydrate availability could be mechanistically linked to ecological dominance via heightened territory defense, increased protein foraging, and colony growth. Supplementation increased aggressive defense of hosts after only two weeks, but was also strongly linked to variation in rainfall. Contrary to predictions, we did not find that supplemented colonies increased protein foraging. Instead, colonies with reduced carbohydrate access discovered a greater proportion of protein baits, suggesting that carbohydrate deprivation increases foraging intensity. We found no significant effect of carbohydrate manipulation on brood or alate production. These results contrast with findings from several recent short-term and lab-based nutrient supplementation studies and highlight the role of seasonality and biotic context in colony-foraging and reproductive decisions. These factors may be essential to understanding the consequences of carbohydrate access in natural plant-ant systems.

Mistletoes represent the best example of specialization in seed dispersal, with a reduced assemblage of dispersal agents. Specific dispersal requirements mediated by the specificity of seed deposition site have apparently led to the evolution of such close relationships between mistletoes and certain frugivores. Here, we provide evidences for another case of specialization involving epiphytic cacti in the genus Rhipsalis, and small Neotropical passerines Euphonia spp., which also act as the main seed dispersers of mistletoes in the family Viscaceae. With field observations, literature search, and observations on captive birds, we demonstrated that Rhipsalis have specific establishment requirements, and euphonias are the most effective dispersers of Rhipsalis seeds in both quantitative and qualitative aspects, potentially depositing seeds onto branches of host plants. We interpret the similar dispersal systems of Rhipsalis and Viscaceae mistletoes, which involve the same dispersal agents, similar fruit morphologies, and fruit chemistry as convergent adaptive strategies that enable seeds of both groups to reach adequate microsites for establishment in host branches.

As ervas-de-passarinho representam o melhor exemplo de especialização em sistemas de dispersão de sementes, apresentando um conjunto reduzido de agentes dispersores. Requisitos específicos de dispersão mediados pela especificidade do local de deposição das sementes aparentemente levou à evolução de relações estreitas entre as ervas-de-passarinho e certos frugívoros. Aqui nós fornecemos evidências para um outro caso de especialização envolvendo cactos epífitos do gênero Rhipsalis e gaturamos (Euphonia spp.), pequenos pássaros das florestas neotropicais que também atuam como os principais agentes dispersores das ervas-de-passarinho da família Viscaceae. Com observações de campo, pesquisa bibliográfica e observações de aves em cativeiro demonstramos que Rhipsalis têm requisitos específicos de estabelecimento, e os gaturamos são os dispersores de sementes mais eficazes de Rhipsalis, tanto em aspectos quantitativos quanto qualitativos, depositando as sementes em ramos de potenciais forófitos. Interpretamos as similaridades nos sistemas de dispersão de Rhipsalis e as Viscaceae, que envolvem os mesmos agentes dispersores e similaridades na morfologia e composição química dos frutos, como estratégias adaptativas convergentes que permitem que as sementes de ambos os grupos cheguem a locais adequados para estabelecimento em ramos de hospedeiros e forófitos.

Logging in tropical forests may create large canopy openings. These gaps provide suitable conditions for some opportunistic shrubs and herbs to take advantage of the surge in resources and rapidly colonize disturbed sites. This dense plant cover may limit forest regeneration by interfering with tree seedling establishment, growth, and survival by altering the light and nutrients available to seedlings, modifying herbivore behavior, or a number of other factors. In Kibale National Park (Uganda), old logging sites are mainly covered by dense stands of Acanthus pubescens Engl., which appear to inhibit tree regeneration. We wanted to identify the ecological processes underlying this regeneration collapse. To do so, we designed a factorial experiment to evaluate the influences of herbivory and vegetation cover on the growth and survival of tree seedlings. We compared the survival and growth of transplanted tree seedlings in A. pubescens stands and logged forests, in the presence or absence of the understory vegetation layer (logged forest) or vegetation cover (A. pubescens), and with or without herbivory. We found no evidence to support the hypothesis that herbivory is significantly higher under dense A. pubescens cover. Seedling survival was not influenced by the environment. Seedling growth, however, was positively influenced by the removal of A. pubescens, suggesting that changes in resource availability associated with the presence of A. pubescens, may be important for regeneration. Our results suggest that sustained cutting of A. pubescens cover could foster the growth of established seedlings and could lead to tree regeneration and habitat restoration.

L'exploitation industrielle des forêts tropicales crée des ouvertures substantielles dans la canopée, ce qui offre des conditions propices à quelques espèces arbustives et herbacées opportunistes qui profitent de l'afflux de ressources pour coloniser massivement les sites perturbés. Ce dense couvert de végétation peut limiter la régénération forestière en interférant avec l'établissement, la croissance et la survie de plantules via l'altération de la disponibilité de lumière et de nutriments ou la modification du comportement des herbivores. Au Parc National de Kibale (Ouganda), d'anciens sites d'exploitation forestière sont principalement couverts de denses peuplements d'Acanthus pubescens Engl., qui semblent inhiber la régénération des espèces arborescentes. Nous avons tenté d'identifier les processus écologiques responsables de cet arrêt de la régénération. Pour ce faire, nous avons réalisé une expérience pour évaluer l'influence de l'herbivorie et du couvert végétal sur la croissance et la survie des plantules. Nous avons comparé la survie et la croissance de plantules transplantées dans les peuplements d'Acanthus avec celles de plantules transplantées en forêts secondaires; en présence ou en absence de couvert végétal et d'herbivorie. Nous n'avons observé aucun effet significatif de la protection des plantules contre l'herbivorie. Toutefois, la croissance des plantules a été positivement influencée par l'élimination du couvert d'Acanthus, ce qui suggère que le changement dans la disponibilité des ressources associé à la présence d'Acanthus peut être un facteur important dans la dynamique de régénération dans cet environnement. Nos résultats suggèrent que la coupe répétée d'Acanthus pourrait favoriser la croissance des plantules, menant à la restauration de l'écosystème forestier.

Golden-headed lion tamarins (GHLTs; Leontopithecus chrysomelas) are endangered primates endemic to the Brazilian Atlantic Forest, where loss of forest and its connectivity threaten species survival. Understanding the role of habitat availability and configuration on population declines is critical for guiding proactive conservation for this, and other, endangered species. We conducted population viability analysis to assess vulnerability of ten GHLT metapopulations to habitat loss and small population size. Seven metapopulations had a low risk of extirpation (or local extinction) over the next 100 years assuming no further forest loss, and even small populations could persist with immediate protection. Three metapopulations had a moderate/high risk of extirpation, suggesting extinction debt may be evident in parts of the species’ range. When deforestation was assumed to continue at current rates, extirpation risk significantly increased while abundance and genetic diversity decreased for all metapopulations. Extirpation risk was significantly negatively correlated with the size of the largest patch available to metapopulations, underscoring the importance of large habitat patches for species persistence. Finally, we conducted sensitivity analysis using logistic regression, and our results showed that local extinction risk was sensitive to percentage of females breeding, adult female mortality, and dispersal rate and survival; conservation or research programs that target these aspects of the species’ biology/ecology could have a disproportionately important impact on species survival. We stress that efforts to protect populations and tracts of habitat of sufficient size throughout the species’ distribution will be important in the near-term to protect the species from continuing decline and extinction.

Micos-leões-da-cara-dourada (MLCDs; Leontopithecus chrysomelas) são primatas ameaçadas de extinção, endêmicas da Mata Atlântica brasileira, onde a perda de cobertura e conectividade das florestas ameaçam a sobrevivência das espécies. Compreender o papel da disponibilidade de habitat e sua configuração no declínio populacional é fundamental para orientar medidas de conservação proativa para esta e outras espécies ameaçadas de extinção. Conduzimos Análise de Viabilidade Populacional para avaliar a vulnerabilidade de 10 metapopulações de MLCDs à perda de habitat e tamanho populacional reduzido. Sete metapopulações tiveram um baixo risco de extirpação (ou extinção local) ao longo dos próximos 100 anos assumindo que não há mais perda de floresta, e até mesmo pequenas populações conseguirão persistir dado proteção imediata. Três metapopulações tiveram um risco moderado/elevado de extirpação, sugerindo ′dívida de extinção′ pode ser evidente em parte da área de distribuição da espécie. Se o desmatamento for continuar no ritmo atual, o risco de extirpação aumenta significativamente enquanto a abundância e diversidade genética diminuirão para todos os metapopulações. Houve correlação significativa negativa entre o risco de extirpação e o tamanho do maior fragmento disponível para metapopulações, ressaltando a importância de grandes áreas de habitat para a persistência da espécie. Por fim, conduzimos uma análise de sensibilidade utilizando regressão logística: os resultados mostraram que o risco de extinção local era sensível a porcentagem de fêmeas reprodutoras, mortalidade fêmea adulta, e a taxa de dispersão e sobrevivência. Programas de conservação ou pesquisa visando estes aspectos da biologia/ecologia da espécie poderiam ter um impacto desproporcionalmente importante na sobrevivência das espécies. Ressaltamos que os esforços para proteger populações e áreas de habitat de tamanho suficiente em toda a área de distribuição da espécie serão importante no curto prazo para proteger a espécie de declínio continuo e extinção.

Sprouting ability is highly variable among different tree species. In many cases, there are trade-offs in carbon allocations between growth and storage in seedlings. However, this trade-off is likely to change with growth stages from seedling to mature plant because carbon investments in reproductive activities and/or risk of disturbance also change by species and growth stage. To examine how sprouting ability and carbohydrate storage change with growth stage, we compared two tropical secondary-forest trees, Macaranga bancana and M. gigantea, which have different ecological traits. Maximum tree size and growth rate are higher in M. gigantea. We monitored sprout growth and stored resources, including total non-structural carbohydrate (TNC) and nitrogen in the root, among different tree sizes for 12 months following stem-cutting treatment. Sprouting ability (total sprout mass) and TNC concentrations were significantly higher in small individuals than in larger specimens in both species. TNC concentration decreased in all size classes after stem cutting. Macaranga bancana had greater sprout survivorship than M. gigantea, which had higher sprouting ability in larger tree-size classes. Thus, sprouting ability likely depends on root TNC concentration and tree-size class in both Macaranga species. Higher TNC concentration and sprout survival rates in M. bancana may be related to greater carbon allocation in survival than in growth. This hypothesis is consistent with the ecological traits of M. bancana, such as its growth rate, which was lower than that of M. gigantea.

How strong-beaked frugivores such as parrots affect other frugivores is poorly understood. This study quantitated six indices of habitat quality for the facultatively frugivorous Bananaquit (Coereba flaveola) using two habitat types and three treatments of habitat quality, namely old growth forest versus citrus orchards in Dominica, the latter habitat type with and without parrot frugivory. The study also controlled for elevation, rainfall and citrus fruit maturity. The results indicate that both the quantity of parrot frugivory and fruit maturity at the time of frugivory influenced the habitat quality for Bananaquits. Their abundance was higher, individuals stored more fat, and parasite loads were lower on farms with more parrot frugivory. Fruit quality mediated the influence of the quantity of parrot frugivory insofar as Bananaquit body condition was tightly correlated with the fruit chemistry at the time of frugivory or harvest. This study provides empirical evidence of a commensal association and underscores the important ecological role of Neotropical psittacines as mediators of habitat quality for other animal. The findings further suggest that loss of these apex consumers may have triggered previously unappreciated trophic cascades, particularly in island ecosystems lacking large mammalian canopy frugivores.

Although termites are ecosystem engineers in tropical and sub-tropical environments, the study of termite ecology is often constrained by sampling difficulties and a lack of established sampling protocols, particularly for savannas. The efficiency and relevance of different methods along climatic gradients, even within a single biome, is largely unknown. Here, we compare the relative contribution of two commonly used sampling methods, cellulose baits and active searching transects, in quantifying savanna termite diversity along a rainfall gradient in South Africa; sampling was conducted during the wet season across four markedly different savanna types. We also assessed the usefulness of different forms of baiting techniques. The relative efficiency of sampling method varied with annual rainfall. In arid savannas, baiting was as effective as active searching transects at sampling termite diversity and we recommend the use of baiting rather due to it being less labor intensive. In savannas of moderately low to intermediate rainfall, baiting and transects sampled different termite species and so both are deemed necessary for an accurate assessment of termite diversity. In contrast, in wetter savannas transects gave a better assessment of diversity, with cellulose baits not contributing much to diversity assessment. The efficiency of baiting techniques differed across the rainfall gradient, with baits needing to be left in the field for a longer period in more arid savannas. We conclude that habitat type, even within a single biome, will determine the sampling method or methods necessary to quantify termite diversity accurately.

Understanding species-specific habitat selection is essential to identify how natural systems are assembled and maintained, and how emerging natural and anthropogenic disturbances will affect ecosystem function. In the Neotropics, Peter's tent-roosting bat (Uroderma bilobatum), known to roost in forests, has become abundant in human-modified areas. To understand how habitat characteristics in both intact forest and human-modified areas influence the presence and density of U. bilobatum, we characterized habitat use at two scales (macrohabitat and microhabitat) and used logistic and poisson regressions to determine which habitat characteristics best predicted the presence and density of U. bilobatum within each scale. Moreover, we performed a redundancy analysis to determine which habitat scale explained more variation. As these bats are obligate tent roosters, we used tent as a surrogate for bat presence and density. We found that both macrohabitat and microhabitat scales explained variation in presence and density. Characteristics of the microhabitat scale, however, had higher predictive power, revealing that U. bilobatum preferentially inhabits areas with high density of coconut palms. Coconut palms were introduced recently in the Neotropics and are found only in human-modified areas. Therefore, we hypothesize that U. bilobatum is expanding its range into these areas following the expanded distribution of this exotic plant species.

Estudiar la selección de habitat de especies específicas, es esencial no sólo para comprender el ensamblaje de sistemas naturales y su mantenimiento, sino también para enclarecer el efecto de perturbaciones antropogénicas en el funcionamiento del ecosistema. En el Neotrópico, el murciélago constructor de tiendas, Uroderma bilobatum, conocido por forrajear y habitar bosques; recientemente se ha tornado abundante en áreas rurales y urbanas. En este studio caracterizamos el uso del hábitat en 2 diferentes escalas (macrohábitat y microhábitat) y utilizamos regresiones logísticas y de Poisson para determinar cuales características del hábitat son más importantes en predecir presencia y densidad. Además, realizamos un análisis de redundancia para determinar cual escala del hábitat explica mayor varianza. Ya que estos murciélagos sólo utilizan tiendas como refugios, utilizamos la presencia y densidad de tiendas como indicador de presencia y densidad de murciélagos. Encontramos que tanto el macrohábitat como el microhábitat pueden explicar varianza en presencia y densidad de murciélagos. Sin embargo, variables dentro de la escala de microhábitat tuvieron mayor poder predictivo, revelando que U. bilobatum habita preferentemente zonas con alta densidad de palmas de coco. Las palmas de coco fueron introducidas recientemente en el Neotrópico y sólo se encuentran en áreas alteradas. Por lo tanto, hipotetizamos que la introducción y abundancia de cocos ha facilitado que U. bilobatum haya ampliado su distribución a áreas alteradas.

Herbivores can both consume and facilitate primary producers with important consequences for community structure. How differences in herbivore foraging ecology alter the relative importance of such effects is not well understood, especially in tropical lentic systems. To address this issue, we manipulated the density of two herbivores with different foraging strategies to evaluate their effects on primary producers and other consumers. Specifically, we examined the effects of the tadpoles of two common Neotropical hylid frogs at two densities on conspecific growth, periphyton and phytoplankton, and zooplankton. We found that the tadpoles of the pantless treefrog, Dendropsophus ebraccatus, reduced periphyton and increased phytoplankton abundances, whereas they had no affect on zooplankton. The red-eyed treefrog, Agalychnis callidryas, also reduced periphyton and increased phytoplankton, but to a greater extent, and they also had strong impacts on zooplankton by altering the composition, size structure, and total abundances of the zooplankton community. Differences between both species' impacts on these food webs were independent of tadpole biomass, as size-selective filter feeding and nutrient cycling seems to drive the impacts of A. callidryas on phytoplankton and zooplankton, while the role of D. ebraccatus is more limited. Species level differences in the strength and direction of top-down and bottom-up effects on food webs suggest that the ecological roles of tadpoles may be diverse and important to aquatic communities.

Herbívoros pueden consumir y facilitar a los productores primarios con importantes consecuencias para la estructura de las comunidades. Sin embargo, los efectos de diferentes estrategias de forrajeo de herbívoros no han sido estudiados con mucha frecuencia, en particular para sistemas lénticos tropicales. Por esta razón, manipulamos la densidad de dos herbívoros con diferentes estrategias de forrajeo para evaluar sus efectos en los productores primarios y otros consumidores. Específicamente, examinamos los efectos de los renacuajos de dos ranas Neotropicales hylid comunes en dos densidades de población en competencia intraespecífico, perifiton, fitoplancton y zooplancton. Encontramos que los renacuajos de Dendropsophus ebraccatus redujeron perifiton y aumentaron abundancia fitoplancton pero no afectaron el zooplancton. Agalychnis callidryas también redujeron perifiton y aumentaron fitoplancton pero más que D. ebraccatus y redujeron la abundancia total de zooplancton y también cambiaron la composición y la estructura de tamaño de su comunidad. Las diferencias entre las especies en sus impactos de estas cadenas alimentarias fueron independientes de la biomasa y parece que la alimentación con filtro selectiva por el tamaño y la excreta de nutrientes causan los impactos de A. callidryas, mientras los impactos de D. ebraccatus son más limitados. Las diferencias en la fuerza y dirección entre los especies en sus efectos en fitoplancton, periphyton y zooplancton sugieren que los efectos ecológicos de renacuajos pueden ser diversos y son importantes para comunidades acuáticas.

Animals modify their foraging strategies in response to environmental changes that affect foraging performance. In some species, cleptobiosis represents an alternative strategy for resource access. The environmental factors that favor the incidence or prevalence of cleptobiosis, however, are poorly described. The cleptobiotic Neotropical ant Ectatomma ruidum is characterized by a high frequency of thievery behavior, a specific type of intraspecific cleptobiosis, in which specialized thief workers insinuate themselves into nests of neighboring colonies and intercept food items brought into these nests. Here, we evaluate how colonies adjust thievery behavior in response to food availability. We supplemented food availability and measured how the incidence and intensity of thievery responded to resource availability. We found that the incidence and intensity of thievery decline in response to supplemental food, suggesting that thievery behavior is a response to resource limitation at the population scale. This finding indicates that the phenomenon of intraspecific thievery, although a rare strategy in among colonies of social animals, is a viable alternative foraging tactic in the context of competition and food limitation.

Los animales cambian sus estrategias de forraje respondiendo a los cambios del ambiente que afectan su modo de rebuscar su alimentación. En algunas especies, la cleptobiosis representa una maniobra alternativa para obteneer los mismos recursos. Sinembargo, los factores medioambientales que favorecen la incidencia o el predomino de la cleptobiosis estan muy pobremente explicados. La hormiga cleptobiotica Neotropical Ectatomma ruidum es caracterizada por una alta frecuencia de una conducta inclinada al robo, tipo especial de la cleptobiosis intraespecifica, el cual los obreros cleptomanos se infiltran en los nidos de las colonias lindantes y se apoderan de los articulos alimenticios traidos a estos lugares. A continuación evaluamos el como las colonias se acomodan a la conducta cleptomana segun la disponibilidad del alimento.Complementamos el alimento disponible y medimos como la ocurrencia e intensidad del robo respondia a la disponibilidad del alimento. Encontramos que la ocurrencia y la intensidad del robo disminuya de acuerdo con el aumento de alimento disponible, sugiriendo que el comportamiento cleptomano es una respuesta a la riqueza limitada de recursos en la escala poblacional. Este descubrimiento indica que el fenomeno de latrocinio intraespecifico, aunque una rara estrategia entre las colonias de animales sociables, es una tactica viable como alternativa en los distintos modos de forrejear alimento en el tratado de competencia y limite alimenticio.

In spite of their recognized importance as seed dispersers in other parts of the tropics, seed dispersal by fruit bats has received scant research attention in Africa. To evaluate the role of African fruit bats in seed dispersal, we studied fruits and seeds below 480 bat feeding roosts in the East Usambara Mountains of Tanzania. We compared these findings to those reported in other African localities to place our results in a broader context. We found 49 plant species dispersed by bats: 28 species, 18 genera, and one family are novel reports of bat dispersal in Africa. Approximately 20 percent of the submontane tree flora of the East Usambaras is bat-dispersed, including both widespread and endemic trees. African fruit bats are important seed dispersers at our study site because they move seeds of dozens of species tens or hundreds of meters, even seeds that are too large to ingest (greater than 5 mm in length). Fruit bats are likely important seed dispersers in other Afrotropical forests, as bats elsewhere in Africa are known to consume 20 genera and 16 species of plants reported here. Insights from studying remains under bat feeding roosts offer a simple method to further document and substantially increase our understanding of the role of African fruit bats in seed dispersal.

Decreases in rainfall have been proposed to have a negative impact on tropical rain forests, and West Africa is currently experiencing a decline in rainfall at the multi-decadal scale. Here, we present analyses of a long-term dataset on the plant fruiting status from individuals of 44 species of the tropical rain forest of Taï National Park, Côte d'Ivoire. This study includes records of 1401 individuals collected at monthly intervals for over 12 yr, 984 of which survived throughout the entire study period. The aims of this study were to: (1) quantitate inter-annual trends in species and forest scale fruit presence; and (2) test the importance of rainfall in explaining inter-annual fruit presence variability. Long-term upward trends in the expected proportion of individuals with fruits were found for the majority of species, while no significant downward trends were detected, driving a significant upward trend at the community level. Peak production months of the upward trending species were not associated with the dry or wet season. Significant rainfall correlations with the total proportion of individuals showing fruit were generally negative, with only five species showing significant positive correlations. Taken together, these results suggest that the observed inter-annual trends and variability of fruit abundance are currently not associated with rainfall. We discuss several parsimonious and complex alternative explanations.

Il a été proposé qu'une diminution des précipitations ait un effet négatif sur les forêts tropicales. Actuellement, les précipitations diminuent à l'échelle multi-décennale en Afrique de l'Ouest. Nous présentons les analyses faites à partir d'un ensemble de données recueillies sur une longue période temporelle décrivant l'état de fructification de plantes individuelles provenant de 44 espèces de la forêt tropicale au Parc National de Taï, Côte d'Ivoire. Cette étude comprend le suivi temporel de 1401 individus échantillonnés à des intervalles mensuels pendant plus de 12 ans, parmi lesquels 984 individus ont survécu tout au long de la période d'étude. L'étude a pour objectifs de: (1) quantifier les tendances interannuelles chez les espèces quant à la présence de fruits à l'échelle de la forêt; et (2) tester l'importance des précipitations pour expliquer les variations interannuelles observées dans la présence de fruits. Des tendances à long terme à la hausse dans la proportion attendue d'individus portant des fruits ont été trouvées pour la majorité des espèces, alors que des tendances à la baisse significatives n'ont pas été détectées, aboutissant à une tendance à la hausse significative au niveau de la communauté. Les mois de production maximale des espèces montrant une tendance à la hausse ne sont pas associés à la saison sèche ou humide. Des corrélations importantes entre les précipitations et la proportion totale d'individus portant des fruits sont généralement négatives, avec seulement cinq espèces montrant des corrélations positives significatives. Pris ensemble, ces résultats suggèrent que les tendances interannuelles observées et les variations de l'abondance de fruits ne sont pas associées aux précipitations. Nous discutons de plusieurs explications alternatives parcimonieuses et complexes.

Habitat heterogeneity may affect the structure of animal assemblages even within apparently homogenous landscapes. Gallery forests of the Amazonia-Cerrado ecotone have a small-scale patchiness that is induced by river system dynamics. Gallery forests that never flood are located in upper areas of watercourse margins, whereas seasonally flooded gallery forests are located at lower ground along those margins. We tested the prediction that the assemblage structure of small non-volant mammals of these two types of forests is distinct and arises from the ecological heterogeneity induced by seasonal floods. We found that species composition differed between forest types, with arboreal species dominating in the seasonally flooded forests and a more balanced distribution of arboreal and terrestrial species in unflooded forests. We found no differences in species abundance between habitats, but species richness was higher in unflooded forests. We hypothesize that this difference is due to decreased resource availability for strictly terrestrial species in seasonally flooded forests. Relative biomass of seasonally flooded forests was more than twice that of unflooded forests due to the dominance of large-bodied didelphid species in that assemblage. Our results suggest that the ecological heterogeneity created by seasonal floods is central to maintaining diverse assemblages in this region. The preservation of both unflooded and flooded gallery forests, which are under high human pressure from deforestation, agricultural conversion, and implementation of dams, may be crucial to preserving small mammal diversity at the landscape scale.

A heterogeneidade do habitat pode influenciar a estrutura das comunidades animais mesmo dentro de paisagens aparentemente homogéneas. As matas de galeria do ecótono entre o Cerrado e a Amazônia apresentam uma heterogeneidade à pequena escala induzida pela dinâmica do sistema aluvial, com matas de galeria que nunca alagam, localizadas nas áreas superiores das margens dos rios, e matas de galeria sazonalmente alagadas, localizadas nas partes baixas dessas margens. Neste trabalho, testamos a predição de que a estrutura de comunidades de pequenos mamíferos não-voadores desses dois tipos de florestas é diferente, resultante da heterogeneidade ecológica induzida por inundações sazonais. Descobrimos que a composição de espécies diferiu entre os tipos de floresta, com uma predominância de espécies arbóreas nas florestas sazonalmente alagadas e uma distribuição mais equilibrada de espécies arbóreas e terrestres em florestas não alagáveis​​. Não foram encontradas diferenças na abundância de espécies entre habitats, mas a riqueza de espécies foi maior nas florestas não alagáveis​​. A nossa hipótese é de que essa diferença se deve à diminuição de recursos disponíveis para espécies estritamente terrestres em florestas sazonalmente alagadas. A biomassa relativa das florestas sazonalmente alagadas revelou ser mais do dobro daquela das florestas não alagadas​​, devido à dominância na comunidade de espécies de didelfídeos de grande massa corporal. Os nossos resultados sugerem que a heterogeneidade ecológica criada por inundações sazonais é um factor chave na manutenção da diversidade das comunidades nesta região. A preservação de florestas de galeria alagadas e não alagadas, que estão sob elevada pressão humana devido ao desmatamento, agricultura e implementação de barragens, pode ser crucial para preservar a diversidade de pequenos mamíferos à escala da paisagem.

N₂-fixing trees can affect stream water quality. This has been documented in temperate streams, but not in tropical ones, even though N₂-fixing trees are prevalent in the tropics. We investigated the effects of the introduced, invasive tree, Falcataria moluccana (albizia) on water quality of Hawaiian streams. Nutrient concentrations were measured in reaches above and below F. moluccana-dominated riparian zones of four streams over 14 mo, and benthic algal nutrient limitation was examined in one stream. NO₃⁻+NO₂⁻ concentrations were up to 600 percent higher in reaches below F. moluccana stands than in ones above them. In contrast, dissolved organic nitrogen concentrations were 24 percent lower in most reaches below F. moluccana stands, and NH₄⁺ and particulate nitrogen concentrations were similar above and below the stands. Dissolved organic carbon concentrations were up to 30 percent lower below F. moluccana stands, but particulate carbon concentrations were similar between reaches. Total dissolved phosphorus concentrations were similar above and below F. moluccana stands, whereas H₄SiO₄ concentrations were higher below the stands. In the stream where benthic chlorophyll a was measured, concentrations were three times higher below the F. moluccana stand than above it. Benthic algae were co-limited by nitrogen and phosphorus above the F. moluccana stand, and limited by phosphorus below it. These results suggest that F. moluccana's presence relieved nitrogen-limitation and caused the benthic algae to become solely phosphorus-limited. Overall, our results demonstrate that F. moluccana can strongly affect the chemistry and primary producers of these tropical streams.

We examined long-term responses of an Amazonian bird assemblage to wildfire disturbance, investigating how understory birds reacted to forest regeneration 1, 3, and 10 years after a widespread fire event. The bird community was sampled along the Arapiuns and Maró river catchments in central Brazilian Amazonia. Sampling took place in 1998, 2000, and 2008 using mist-nets in eight plots (four burned, four unburned sites). Species richness did not change significantly in unburned sites. In burned sites, however, we found significantly lower richness in 1998, higher richness in 2000, and similar richness in 2008. Multi-dimensional scaling ordination showed consistent differences in bird communities both within burned sites sampled in different sampling years, and between burned and unburned sites in all years. Of the 30 most abundant species, 12 had not recovered 10 years after the fires, including habitat specialists such as mixed flocks specialists and ant-followers. Fire-disturbance favored three species (two hummingbirds and a manakin) in the short term only. All other species were either favored throughout the study (seven species of omnivores and small insectivores) or did not show a clear response (eight species). In burned sites, we also found significantly lower abundance of species sensitive to disturbances and habitat specialists over the entire study period. Although the bird community seems to be recovering in terms of richness, the overall community composition and abundance of some species in post-burned and unburned sites remain very different, and have not recovered after 10 years of forest regeneration.

Neste estudo examinamos as respostas das comunidades de aves aos impactos de longo prazo causados por um incêndio florestal na Amazônia Central, investigando como a comunidade de aves de sub-bosque se modifica com a regeneração da floresta queimada depois de um, três e dez anos. A comunidade de aves foi amostrada entre os rios Arapiuns e Maró, na Amazônia Central, Pará, Brasil. As amostragens foram realizadas nos anos de 1998, 2000 e 2008 usando redes-neblina em oito áreas (quatro que foram queimadas e quatro íntegras). Observamos que a riqueza de aves não mudou significativamente nos locais não queimados. No entanto, registramos nos locais regenerados após o incêndio menor riqueza em 1998, maior em 2000 e riqueza similar aos locais íntegros em 2008. A análise de ordenação multidimensional (MDS) mostrou diferenças consistentes na estrutura das comunidades de aves quando comparamos as áreas queimadas e não queimadas. Esta mesma análise também mostrou diferenças estatísticas entre os locais queimados nos diferentes anos de amostragens. Quando comparamos as 30 espécies mais comuns neste estudo, observamos que 12 não tiveram suas abundâncias originais regeneradas mesmo dez anos depois do incêndio florestal, sendo estas principalmente aves especialistas, como espécies de bandos mistos e espécies seguidoras de formigas de correição. Observamos que três espécies parecem ser favorecidas em curto prazo pelas queimadas (dois beija-flores e um tangará). Outras espécies foram favorecidas por este impacto durante os três períodos estudados (sete espécies de onívoros e pequenos insetívoros) ou não tiveram uma resposta clara (oito espécies). Nos locais queimados, observamos durante todos os períodos amostrados menores abundâncias de espécies sensíveis a impactos ambientais e de espécies que vivem em um menor número de habitats (especialistas). Apesar da comunidade de aves parecer estar se recuperando em relação a riqueza de espécies, observamos que a composição da comunidade de aves e a abundância de algumas espécies continua muito diferente da original e ainda não se recuperou de um único evento de incêndio florestal ocorrente a 10 anos atrás.

Hurricanes represent the dominant type of disturbance in many tropical coastal forests. Here, we focus on mortality of epiphytic orchids caused by hurricane Ivan in the Guanahacabibes National Park (Cuba) and subsequent population recovery. We analyzed different aspects of hurricane damage on two contrasting epiphytic orchids, Broughtonia cubensis and Dendrophylax lindenii, as observed in three plots of coastal vegetation and in three plots of semi-deciduous forest, respectively. First, we quantified the damage to host trees and orchids and explored if hurricane damage depended on height, size, or identity of the host tree. Second, we used mark connection and mark correlation functions to conduct a detailed analysis of small-scale spatial patterns in hurricane damage for host trees and orchids. Finally, we analyzed the degree of recovery after Ivan during the 6 yr following the storm. Damage of B. cubensis host trees was independent of height and size, but Ivan severely affected larger and higher host trees of D. lindenii. Spatial analysis revealed non-random structure in damage that differed between species. Broughtonia cubensis exhibited small-scale spatial correlation in the proportion of damaged orchids, whereas D. lindenii did not. Dendrophylax lindenii showed ‘patchy’ damage patterns, correlated with height, but B. cubensis did not. The relative growth rate of B. cubensis for the 5–17 mo following Ivan was only moderately reduced and fully recovered in subsequent years, whereas that of D. lindenii was severely reduced the first year and did not fully recover thereafter. We hypothesize that differences in the host, vegetation type, and the traits of the two orchids contribute to the different responses to the hurricane.

Los huracanes son el tipo dominante de perturbación en muchos bosques costeros tropicales. Aquí nos centramos en la mortalidad de las orquídeas epífitas causados por el huracán Iván en el Parque Nacional de Guanahacabibes (Cuba) y la recuperación de la población posterior. Se analizaron diferentes aspectos de los daños del huracán en dos orquídeas epífitas contrastantes, Broughtonia cubensis y Dendrophylax lindenii, en tres parcelas de vegetación costera y en tres parcelas de bosque semi-caducifolio, respectivamente. En primer lugar, hemos cuantificado el daño en los árboles hospederos de orquídeas. Se exploró si los daños del huracán dependen de la altura, el tamaño o la identidad del árbol huésped. En segundo lugar, hemos utilizado la marca de conexión y funciones de la marca de correlación para llevar a cabo un análisis detallado de los patrones espaciales a pequeña escala de los daños del huracán en árboles hospederos y orquídeas. Por último, se analizó el grado de recuperación después de Iván durante los seis años que siguieron a la tormenta. El daño de los árboles hospederos de B. cubensis fué independiente de la altura y tamaño, sin embargo, Ivan afecta preferentemente a árboles grandes que albergan a D. lindenii. El análisis espacial reveló una estructura no aleatoria del daño que difieren entre las especies. Broughtonia cubensis exhibido a pequeña escala, una correlación espacial en la proporción de orquídeas dañados mientras D. lindenii no lo hizo. Dendrophylax lindenii mostró patrones “irregulares” de daño, en correlación con la altura, no así B. cubensis. La tasa de crecimiento relativo de B. cubensis para los meses siguientes 5–17 al Ivan mostró una reducción moderada y se recuperó en los años siguientes, mientras que la de D. lindenii se redujo drásticamente durante el primer año y aún no muestras síntomas de recuperación. Nuestra hipótesis es que las diferencias en el hospedero, el tipo de vegetación en que viven y las características propias de las orquídeas, condicionan las diferentes respuestas de estas dos orquídeas al huracán.

The Brazilian Atlantic Forest has been replaced by homogeneous tree monocultures with potentially drastic effect on ecological interactions. We expect that ecologically-managed tree monocultures, however, can help to mitigate this impact. Here, we carried out an experiment with Inga vera (Fabaceae), an extrafloral nectary bearing plant, to test if the efficiency of ants as anti-herbivory defense is affected by the replacement of its natural habitat (Araucaria Forest) by ecologically-managed tree monocultures (plantations of Araucaria, Pinus, and Eucalyptus). Seedlings of Inga vera were transplanted to three patches of each habitat and ants were excluded from half of the plants. The abundance of ants and herbivores was low, similar among habitats, and exhibited temporal asynchrony. Number of herbivores and accumulated herbivory levels were lower in plant with ants. Rates of herbivory were extremely low and lower for young leaves than for mature leaves. The presence of ants did not affect plant performance traits measured by their growth in height, and their final numbers of leaves and leaflets. Contrary to what might be expected, ant-protected plants produced fewer leaves and leaflets than unprotected ones. In conclusion, Inga vera-ant interaction was similar between its natural habitat and the tree monocultures, indicating that potentially both species diversity and ecological processes can be conserved in ecologically-managed tree monocultures.

A Mata Atlântica brasileira tem sido substituída por monuculturas florestais gerando potencialmente efeitos drásticos nas interações ecológicas. No entanto, espera-se que o manejo ecológico de monoculturas florestais possa ajudar a aliviar este impacto. Neste estudo, desenvolvemos um experimento com Inga vera (Fabaceae), que apresenta nectários extraflorais, para testar se a eficiência de formigas como defesa anti-herbivoria é afetada pela substituição de seu hábitat natural (Floresta de Araucaria) por monoculturas florestais ecologicamente manejadas (plantações de Araucaria, Pinus e Eucalyptus). Plântulas de Inga vera foram transplantadas para três fragmentos de cada habitat sendo que as formigas foram excluídas de metade das plântulas de cada fragmento. A abundância das formigas e dos herbívoros foi baixa, e semelhante entre hábitats, apresentando uma acentuada assincronia temporal. O número de herbívoros e o nível acumulado de herbivoria foi menor em plantas com formigas. As taxas de herbivoria foram extremamente baixas e mais baixas em folhas jovens do que em folhas maduras. A presença das formigas não influenciou a performance das plantas; a altura, número de folhas e folíolos foram semelhantes em plantas com e sem formiga. No entanto, diferente do esperado, plantas com formigas produziram menos folhas e folíolos do que plantas sem formigas. Os resultados sugerem que mutualismos entre formigas e plantas com nectários extraflorais podem ser conservados em monoculturas florestais ecologicamente manejadas.

The tropics are clearly defined while ‘subtropics’ and ‘subtropical’ have been applied to a variety of zones, climates, and ecosystems. However, in the recent terrestrial biology literature, they have been used mainly for the zones between the tropics (±23.4^oC) and ±30.0^o. Adopting this standard would facilitate pan-subtropical comparisons.

In East Africa, up to four symbiotic ant species associate with the obligate myrmecophyte Acacia drepanolobium. These ant species differ in the extent to which they defend their host trees from both vertebrate and invertebrate herbivores, but other potential roles of ants in tree defense have not been studied. We investigate the distribution of a new species of parasitic midge targeting A. drepanolobium in a region where A. drepanolobium is inhabited almost exclusively by two ant species—Crematogaster nigriceps and C. mimosae. We find that the frequency of infestation correlates strongly with the identity of the ant occupant: trees inhabited by C. nigriceps are significantly less likely to be infested with parasitic midges. Although the two ant species responded similarly to simulated large herbivore disturbances, trees inhabited by C. nigriceps also had a lower invertebrate load than trees inhabited by C. mimosae. We suggest that differences in defensive behavior towards invertebrates could be one explanation of the observed differences in infestation of A. drepanolobium by parasitic midges.

Cell walls, water, and gas that have mechanical and physiological functions in wood, and wood specific gravity (WSG) is related to demographic traits. To understand variation in wood structure and function, we analyzed radial changes in WSG, in the gas and the water fractions from trees growing in four different habitats in a southern Mexican rain forest. Mean WSG was 0.55 ± 0.16, slightly lower than reported for other tropical forests. In 27 species, WSG decreased and in two species, it increased from pith to bark with a strong (r² = 0.65) negative correlation between WSG in the center of the tree and the radial WSG gradient. Habitat had some effect on mean WSG and trees growing on karst had significantly higher WSG than the same species growing on alluvial soil. The cell wall, water, and gas fractions accounted for 35 percent (range: 16–50), 42 percent (28–65), and 23 percent (2–56), respectively, of wood volume, with a negative correlation between the gas and the cell wall and between the gas and the water fractions, but not between the cell wall and water fractions. Radially increasing WSG is advantageous for pioneer trees with fast initial growth. We found that the water displacement method may result in biased WSG estimates. To increase the accuracy of WSG data, we suggest to measure sample volume geometrically using a constant diameter (that of the borer tip), to include radial variation in WSG, and to consider for possible site effects on species-specific WSG.

Las paredes celulares, agua y gas con funciones mecánicas y fisiológicas en la madera y su gravedad específica (GE) están asociadas con rasgos demográficos. Para entender la variación en la estructura de la madera y su función, analizamos variaciones radiales en la GE, gas y proporciones de agua en árboles provenientes de cuatro diferentes hábitats en un bosque tropical lluvioso del Sur de México. La GE media (0.55 ± 0.16) resultó ligeramente más baja que las previamente reportadas para otros bosques tropicales. La GE disminuyó en 27 especies, mientras que en dos especies, ésta incrementó desde la médula hasta la corteza con una alta correlación negativa (r² = 0.65) entre la GE en el centro del árbol y su gradiente radial. Observamos también cierto efecto del hábitat en nuestras mediciones, por ejemplo, los árboles creciendo en terrenos cársticos tenían un GE significativamente más alto que aquellos creciendo en suelos aluviales. La proporción del volúmen de la madera ocupado por paredes celulares fue de 35% (rango: 16–50), de agua de 42% (28–65) y de gas de 23% (2–56). Obtuvimos correlaciones negativas al comparar el gas con la pared celular y el gas con las proporciones de agua, mas no para la pared celular con las proporciones de agua. El aumento radial de la gravedad específica proporciona una ventaja para árboles pioneros con un rápido crecimiento inicial. Encontramos potenciales sesgos del método de desplazamiento del agua en las estimaciones de GE, por lo que sugerimos medir el volumen geométrico de la muestra, usando un diámetro constante (de la punta de la broca), para aumentar la precisión en las estimaciones. También sugerimos incluir la variación radial y potenciales efectos del sitio en la GE de diferentes especies.

A standardized rapid inventory method providing information on both tree species diversity and aboveground carbon stocks in tropical forests will be an important tool for evaluating efforts to conserve biodiversity and to estimate the carbon emissions that result from deforestation and degradation (REDD). Herein, we contrast five common plot methods differing in shape, size, and effort requirements to estimate tree diversity and aboveground tree biomass (AGB). We simulated the methods across six Neotropical forest sites that represent a broad gradient in forest structure, tree species richness, and floristic composition, and we assessed the relative performance of methods by evaluating the bias and precision of their estimates of AGB and tree diversity. For a given sample of forest area, a ‘several small’ (< 1 ha) sampling strategy led to a smaller coefficient of variation (CV) in the estimate of AGB than a ‘few large’ one. The effort (person-days) required to achieve an accurate AGB estimate (< 10% CV), however, was greater for the smallest plots (0.1 ha) than for a compromise approach using 0.5 ha modified Gentry plots, which proved to be the most efficient method to estimate AGB across all forest types. Gentry plots were also the most efficient at providing accurate estimates of tree diversity (< 10% CV of Hill number). We recommend the use of the 0.5 ha modified Gentry plot method in future rapid inventories, and we discuss a set of criteria that should inform any choice of inventory method.

The literature on tropical rain forest plant-community relationships with environmental factors usually does not recognize that the relative importance of environmental factors recorded in each study might be due to their amplitude of variation within sites. Geographic scale, however, is recognized as an important modulator of this relative importance. To disentangle the effects of scale and environmental amplitude, ferns and trees in two landscapes of the same size (each 25 km²) with different soil-fertility amplitudes but similar soil-texture range were sampled in central Amazonia. We found that major determinants of community structure were the same for ferns and trees. Texture was the main predictor of community structure in the site with homogeneous soil fertility, while availability of exchangeable cations was the main predictor in the site with a wider fertility range. When both sites were analyzed together, soil fertility was the main predictor of community structure and soil texture segregated floristic subgroups within certain ranges of the soil-fertility gradient. We conclude that: (1) floristic patterns for trees and ferns are congruent; (2) floristic variation depends on the amplitude of the studied gradients, more than on geographical scale; (3) limiting factors are not necessarily the most important predictors of compositional patterns; and (4) communities are structured hierarchically. Therefore, landscape structure (meaning which combinations of environmental factors, their amplitude of variation and which part of the gradient is found within the landscape) affect our perception of the relative importance that environmental factors will have as predictors of species composition.

A literatura sobre as relações entre plantas de florestas tropicais e fatores ambientais geralmente não leva em conta que a importância relativa dos fatores ambientais registrada em cada estudo pode ser devida à sua amplitude de variação dentro de cada área. A escala geográfica, no entanto, é reconhecida como uma importante moduladora dessa importância. Para separar os efeitos da escala e da amplitude do gradiente, samambaias e árvores de duas paisagens do mesmo tamanho (25 km² cada), com diferentes amplitudes na fertilidade do solo, mas com textura do solo semelhante foram amostradas na Amazônia central. Os principais determinantes da estrutura da comunidade foram os mesmos para as samambaias e as árvores. A textura do solo foi o principal preditor da estrutura da comunidade na área com fertilidade do solo homogênea, enquanto a disponibilidade de cátions trocáveis ​​foi o principal preditor no local com maior amplitude de fertilidade. Quando ambos os locais foram analisados ​​em conjunto, a fertilidade do solo foi a principal determinante da estrutura da comunidade e a textura do solo segregou subgrupos florísticos dentro do gradiente de fertilidade do solo. Conclui-se que: (1) padrões florísticos para árvores e samambaias são congruentes; (2) a variação florística depende da amplitude dos gradientes estudados, mais do que da escala geográfica; (3) fatores limitantes não são necessariamente os mais importantes preditores de padrões de composição; e (4) as comunidades são estruturadas hierarquicamente. Portanto a estrutura da paisagem (ou seja, as combinações de fatores ambientais, sua amplitude de variação e que partes do gradiente são encontradas dentro da paisagem) afeta definitivamente a nossa percepção da importância relativa que os fatores ambientais terão como preditores da composição de espécies.

The spatial arrangement of tree species is a key aspect of community ecology. Because tree species in tropical forests occur at low densities, it is logistically challenging to measure distributions across large areas. In this study, we evaluated the potential use of canopy tree crown maps, derived from high-resolution aerial digital photographs, as a relatively simple method for measuring large-scale tree distributions. At Barro Colorado Island, Panama, we used high-resolution aerial digital photographs (~0.129 m/pixel) to identify tree species and map crown distributions of four target tree species. We determined crown mapping accuracy by comparing aerial and ground-mapped distributions and tested whether the spatial characteristics of the crown maps reflect those of the ground-mapped trees. Nearly a quarter (22%) of the common canopy species had sufficiently distinctive crowns to be good candidates for reliable mapping. The errors of commission (crowns misidentified as a target species) were relatively low, but the errors of omission (missed canopy trees of the target species) were high. Only 40 percent of canopy individuals were mapped on the air photographs. Despite failing to accurately predict exact abundances of canopy trees, crown distributions accurately reproduced the clumping patterns and spatial autocorrelation features of three of four tree species and predicted areas of high and low abundance. We discuss a range of ecological and forest management applications for which this method can be useful.

Un aspecto clave en ecología de comunidades es la distribución espacial de especies de arboles. Sin embargo, debido a que estas especies se encuentran en bajas densidad en los bosques tropicales, es logísticamente exigente medir su distribución en grandes áreas. En este estudio, evaluamos el uso potencial de mapas de la copa de arboles del dosel, derivados de fotos digitales aéreas de alta resolución, como un método relativamente simple de medir distribuciones de arboles a gran escala. En la Isla de Barro Colorado, Panamá, utilizamos fotografías digitales aéreas de alta resolución (~0.129 m/pixel) para identificar especies, y mapear la distribución de las copas de cuatro especies de arboles. Determinamos la precisión de estos mapas, comparando distribuciones mapeadas desde aire y tierra, y verificamos si los mapas de distribución de copas de arboles reflejan los patrones espaciales de los arboles mapeados desde tierra. Casi un cuarto (22%) de las especies de dosel comunes tuvieron copas suficientemente distintivas para ser mapeadas confiablemente. Los errores de comisión (copas identificadas como una especie no eran esa especie) fueron relativamente pocos, pero los errores de omisión (copas de una especie no identificadas) fueron altos. Solo el 40% de los individuos en el dosel fueron mapeados con las fotos aéreas. A pesar de fallar al predecir con precisión las abundancias exactas de los arboles de dosel, los mapas de distribución de copas reprodujeron con precisión los patrones de agregación y las características de correlación espacial en tres de cuatro especies y sirvieron para estimar áreas de alta y baja abundancia de individuos. Adicionalmente, discutimos el rango de aplicaciones ecológicas y de manejo de bosques para las cuales este método puede ser útil.

Recent evidence suggests that liana abundance and biomass are increasing in Neotropical forests, representing a major structural change to tropical ecosystems. Explanations for these increases, however, remain largely untested. Over an 8-yr period (1999–2007), we censused lianas in nine, 24 × 36 m permanent plots in old-growth and selectively logged forest at La Selva Biological Station, Costa Rica to test whether: (1) liana abundance and basal area are increasing in this forest; (2) the increase is being driven by increased recruitment, decreased mortality, or both; and (3) long-distance clonal colonization explains the increase in liana abundance and basal area. We defined long-distance clonal colonization as lianas that entered and rooted in the plots as vegetative propagules of stems that originated from outside or above the plot, and were present in 2007, but not in 1999 or 2002. Our hypotheses were supported in the old-growth forest: mean liana abundance and BA (≥1 cm diameter) increased 15 and 20 percent, respectively, and clonal colonization from outside of the plots contributed 19 and 60 percent (respectively) to these increases. Lianas colonized clonally by falling vertically from the forest canopy above or growing horizontally along the forest floor and re-rooting—common forms of colonization for many liana species. In the selectively logged forest, liana abundance and BA did not change, and thus the pattern of increasing lianas may be restricted to old-growth forests. In summary, our data support the hypothesis that lianas are increasing in old-growth forests, and that long-distance clonal colonization is a major contributor.

Actualmente existe evidencia sustancial de que la abundancia y la biomasa de lianas en bosques tropicales va en aumento, lo cual es un cambio estructural profundo para estos ecosistemas. Sin embargo, hay pocas explicaciones para este fenómeno. Durante 8 años (1999–2007), hicimos un inventario de lianas en nueve parcelas permanentes de 24 × 36 m en un bosque primario y un bosque intervenido en la Estación Biológica La Selva, Costa Rica, para indagar (1) si la abundancia y la biomasa de lianas en este bosque han aumentado; (2) si el aumento ocurre gracias a un mayor reclutamiento, a una menor mortalidad, o por ambos mecanismos; y (3) si la colonización clonal de larga distancia explica el aumento de la abundancia y la biomasa. Definimos la colonización clonal de larga distancia como el reclutamiento de lianas que entraron a las parcelas y se establecieron como propágulos vegetativos de tallos que se originaron afuera de o arriba de las parcelas (i.e. echaron raices), y que estaban presentes en 2007 pero ausentes en 1999 y 2002. Hayamos evidencia para apoyar para nuestras hipótesis en el bosque primario: el diámetro promedio de las lianas aumentó en un 15%, el área basal de lianas ≥1cm diámetro aumentó en un 20%. La colonización clonal contribuyó en un 19% y 60%, respectivamente, de esos aumentos. Las lianas colonizaron las parcelas al caer verticalmente del dosel o por crecer horizontalmente sobre el suelo y luego echar raíces; formas comunes de colonización para muchas especies de lianas. En el bosque intervenido, no se presentaron cambios ni en la abundancia ni en la biomasa de lianas, así que el patrón de aumento podría ser un fenómeno restringido al bosque maduro. En resumen, los datos apoyan la hipótesis de que las lianas están aumentando en el bosque primario, y que la colonización clonal es un mecanismo importante.

Plant reproductive success is usually positively related to conspecific floral density, but neutral or negative effects of floral density on reproduction have also been reported. Differences in the relationship between reproduction and floral density largely originate from a trade-off between increasing attractiveness versus increasing competition for pollinators at high floral densities. Although floral densities strongly vary in the understory of tropical forests, for instance, due to variation in light availability, little is known about the density dependence of reproduction in tropical understory plants. We used path analyses to disentangle direct and indirect effects of canopy openness and floral density on fruit set and analyzed the relationship between pollen load and floral density for two Neotropical understory plants, Heliconia metallica and Besleria melancholica. In both species, fruit set was not directly related to canopy openness, but decreased with increasing floral density. In H. metallica, canopy openness had an indirect negative effect on reproduction mediated by its effects on floral density. Effects of floral density on pollen loads were species-specific. In B. melancholica, pollen loads linearly decreased with increasing floral density, indicating competition for pollinators at high densities. In H. metallica, pollen loads were reduced at both low and high densities, indicating an interplay of facilitative and competitive effects of floral density on pollen deposition. In contrast to other studies, we found negative density dependence of reproduction in both understory species. Negative effects of floral density on reproduction appear to be related to pollinator-mediated effects on reproduction rather than to variation in abiotic conditions.

El éxito reproductivo en la planta suele estar relacionada positivamente con la densidad co-especifica floral aunque también se han reportado los efectos neutros o negativos de la densidad floral en la reproducción. Las diferencias en la relación entre la reproducción y la densidad floral en gran parte provienen del ‘trade-off’ entre el atractivo cada vez mayor versus la creciente competencia por los polinizadores a altas densidades florales. Aunque las densidades florales varían fuertemente en el sotobosque de los bosques tropicales, por ejemplo debido a la variación en la disponibilidad de luz, poco se sabe acerca de la dependencia de la densidad de la reproducción en las plantas del sotobosque tropical. Se utilizó análisis de trayectoria para separar los efectos directos e indirectos de la apertura del dosel y la densidad floral en la maduración y se analizó la relación entre la carga y la densidad de polen floral para dos plantas de sotobosque neotropical, Heliconia metallica y Besleria melancholica. En ambas especies, la maduración no estaba directamente relacionada con la apertura del dosel, pero disminuyó al aumentar la densidad floral. En H. metallica, la apertura del dosel tuvo un efecto negativo indirecto sobre la reproducción mediada por sus efectos sobre la densidad floral. Efectos de la densidad floral en las cargas de polen son específicos de cada especie. En B. melancholica, las cargas de polen disminuyeron linealmente al aumentar la densidad floral, lo que indica la competencia por los polinizadores en altas densidades. En H. metallica, cargas de polen se redujeron en ambas densidades altas y bajas, lo que indica una interacción de los efectos de facilitación y competitivo de la densidad floral sobre la deposición de polen. En contraste con otros estudios, encontramos dependencia de la densidad de la reproducción negativa en ambas especies del sotobosque. Los efectos negativos de la densidad floral en la reproducción parecen estar relacionados con los efectos mediados por los polinizadores sobre la reproducción en lugar de la variación en las condiciones abióticas.

In Neotropical forests, mammals act as seed dispersers and predators. To prevent seed predation and promote dispersal, seeds exhibit physical or chemical defenses. Collared peccaries (Pecari tajacu) cannot eat some hard seeds, but can digest chemically defended seeds. Central American agoutis (Dasyprocta punctata) gnaw through hard-walled seeds, but cannot consume chemically defended seeds. The objectives of this study were to determine relative peccary and agouti abundances within a lowland forest in Costa Rica and to assess how these two mammals affect the survival of large seeds that have no defenses (Iriartea deltoidea, Socratea exorrhiza), physical defenses (Astrocaryum alatum, Dipteryx panamensis), or chemical defenses (Mucuna holtonii) against seed predators. Mammal abundances were determined over 3 yrs from open-access motion-detecting camera trap photos. Using semi-permeable mammal exclosures and thread-marked seeds, predation and dispersal by mammals for each seed species were quantified. Abundances of peccaries were up to six times higher than those of agoutis over 3 yrs, but neither peccary nor agouti abundances differed across years. Seeds of A. alatum were predominantly dispersed by peccaries, which did not eat A. alatum seeds, whereas non-defended and chemically defended seeds suffered high levels of predation, mostly by peccaries. Agoutis did not eat M. holtonii seeds. Peccaries and agoutis did not differ in the distances they dispersed seeds. This study shows that seed fates are contingent upon many factors such as seed defenses, frugivore–granivore abundances, and seed-handling capabilities. Mammal–seed interactions are complex; the outcomes of these interactions depend on the inherent characteristics of seeds and their potential dispersers.

En bosques neotropicales, los mamíferos pueden jugar al mismo tiempo el papel de dispersores o depredadores de semillas. Para evitar la depredación y promover su dispersión, las semillas presentan defensas químicas y mecánicas. El saíno (Pecari tajacu) no puede comer semillas duras, pero puede digerir semillas con defensas químicas. La guatusa (Dasyprocta punctata) roe atreves de los endocarpos leñosos de las semillas, pero no puede consumir semillas con defensas químicas. Los objetivos de este estudio incluyen: determinar la abundancia relativa de saínos y guatusas en un bosque húmedo tropical de tierras bajas en Costa Rica y determinar cómo estos dos mamíferos afectan la supervivencia de semillas de gran tamaño sin defensas (Iriartea deltoidea, Socratea exorrhiza), que presentan defensas mecánicas (Astrocaryum alatum, Dipteryx panamensis) ó con defensas químicas (Mucuna holtonii). Determiné la abundancia de estos mamíferos por tres años usando cámaras trampa. Usando cercados semipermeables y semillas marcadas, medí la depredación y la dispersión por mamíferos para cada una de estas especies de planta. Los saínos fueron seis veces mas abundantes que las guatusas durante los tres años de muestreo. Las abundancias de saínos y guatusas no cambió en los tres años de estudio. Las semillas de A. Alatum no fueron consumidas y se beneficiaron con la dispersión por los saínos. Las semillas sin defensas y las semillas con defensas químicas sufrieron altos niveles de depredación. Las guatusas no consumieron semillas de M. Holtonii. Los saínos y las guatusas no presentaron diferencias en la distancia de dispersión de las semillas. Este estudio muestra que la efectividad de las defensas de las semillas contra depredadores depende de las abundancias y las características de manipulación de los mamíferos frugívoros-granívoros. Este estudio demuestra que el destino de las semillas depende entre otros factores de las defensas de las semillas, la abundancia de los mamíferos y su habilidad para manipular las semillas. Las interacciones mamífero-semilla son complejas; el resultado de estas interacciones depende de las características intrínsecas de las semillas y de sus potenciales dispersores.

The Atlantic Forest domain, one of the 25 world's hotspots for biodiversity, has experienced dramatic changes in its landscape. While the loss of species diversity is well documented, functional diversity has not received the same amount of attention. In this study, we evaluated functional diversity of insects in streams utilizing three indices: functional diversity (FD), functional dispersion (FDis), and functional divergence (FDiv), seeking to understand the roles of three predictor sets in explaining functional patterns: (1) bioclimatic and landscape variables; (2) spatial variables; and (3) local environmental variables. We determined the amount of variation in different measures of functional diversity that was explained by each predictor set and their interplays using variation partitioning. Our study showed that variation in functional diversity is better explained by a set of variables linked to different scales dependent on spatial structures, indicating the importance of landscape and mainly environmental variables in the functional organization of aquatic insect communities, and that the relative importance of predictor sets depends on the indices considered. Variation in FD was better explained by the interplay among the three predictor sets and by local environmental variables, whereas variation in FDis was better explained by spatial variables and by the interplay between environmental and spatial variables. Variation in FDiv was not significantly explained by any predictors. Our study adds more evidence on the harmful effects caused by landscape changes on biodiversity in the Atlantic Forest, suggesting that these effects also influence the functional organization of stream insect communities.

O domínio da Mata Atlântica, considerado um dos 25 hotspots mundiais de biodiversidade, sofreu mudanças dramáticas em sua paisagem. Embora a perda da diversidade de espécies esteja bem documentada, a diversidade funcional não recebeu a mesma atenção. Neste estudo, avaliamos a diversidade funcional de insetos em córregos utilizando três índices: diversidade funcional (FD), a dispersão funcional (FDis) e divergência funcional (FDiv), buscando entender os papéis de três conjuntos de preditores para explicar padrões funcionais: (1) variáveis de paisagem, formadas por variáveis bioclimáticas, altitude e cobertura florestal, (2) variáveis espaciais, e (3) variáveis ambientais locais. Determinamos a quantidade de variação nas diferentes medidas de diversidade funcional que foi explicada por cada conjunto de preditores e por suas frações compartilhadas usando partição de variância. Em nosso estudo a variação na diversidade funcional foi melhor explicada por um conjunto de variáveis relacionadas com escalas diferentes dependentes da estrutura espacial, indicando a importância da paisagem e principalmente das variáveis ambientais na organização funcional de comunidades de insetos aquáticos, e que a importância relativa dos conjuntos de preditores depende dos índices considerados. A variação em FD foi melhor explicada pela relação entre os três conjuntos de preditores e pelas variáveis ambientais locais enquanto que a variação em FDis foi melhor explicada pelas variáveis espaciais e pela relação entre o meio ambiente local e variáveis espaciais. A variação de FDiv não foi significativamente explicada por nenhum dos preditores utilizados. Nosso estudo adiciona mais evidências sobre os efeitos nocivos causados por alterações da paisagem sobre a biodiversidade da Mata Atlântica, sugerindo que esses efeitos também influenciam a organização funcional das comunidades de insetos nos córregos.

Studies comparing the abundance of frugivorous bats in shade-coffee plantations and forest fragments report contradictory results, and have not taken into account the landscape context in which coffee plantations are immersed. Variables of population composition such as abundance, sex proportion, and reproductive condition, together with biological tags (i.e., bat fly prevalence), can provide information about spatiotemporal dynamics of habitats used by bats. In the central part of Veracruz, Mexico, we compared population variables and ectoparasite prevalence of the highland yellow-shouldered bat (Sturnira ludovici) in two landscapes, one dominated by shade-coffee plantations and another by forest fragments. Comparing these attributes between these two landscapes will increase our knowledge about the role of this agro-ecosystem in the conservation of this species, which is an important seed disperser of cloud forest vegetation. Total abundance and proportion of females was greater in forest fragments than in coffee plantations, whereas the percentage of reproductive females and bat fly prevalence was similar between landscapes. Our results show that landscapes with forest fragments harbor the greatest abundance of S. ludovici, but shade-coffee plantations also are utilized by S. ludovici and likely adjacent forest remnants provide enough food resources for this species and other frugivores. Moreover, this study provides more evidence documenting the importance of preserving the last cloud forest fragments in the central region of Veracruz, Mexico, and suggests that using shade-coffee plantations to connect forest fragments may be an effective way of maintaining populations of S. ludovici and likely other volant frugivores.

Los estudios que comparan la abundancia de murciélagos frugívoros en plantaciones de café y fragmentos de bosque reportan resultados contradictorios y no toman en cuenta el contexto del paisaje donde se encuentran las plantaciones de café. Variables que describen la composición de la población como el sexo y estado reproductivo, así como marcas biológicas (prevalencia de dípteros ectoparásitos) pueden dar información sobre la dinámica espacio-temporal de los hábitats usados por los murciélagos. En el centro de Veracruz, México, comparamos variables de la composición de la población y prevalencia de ectoparásitos del murciélago frugívoro Sturnira ludovici en dos paisajes, uno dominado por cafetales bajo sombra y otro por fragmentos de bosque. La comparación de estos atributos poblacionales entre ambos paisajes ayudaría a aumentar el conocimiento del papel de este agro-ecosistema en la conservación de esta especie importante en la dispersión de arbustos y árboles del bosque de niebla. La abundancia y proporción de hembras fue mayor en fragmentos de bosque, mientras que el número de hembras reproductivas y prevalencia de ectoparásitos fue similar en ambos paisajes. Nuestros resultados sugieren que a pesar de que el paisaje con fragmentos de bosque es el hábitat preferido para S. ludovici, las plantaciones de café bajo sombra también son usados por esta especie, quizás porque los remanentes de bosque adyacentes a los cafetales contienen suficiente alimento para ella y otras especies de murciélagos frugívoros. Así mismo, este estudio provee más evidencia para conservar los últimos fragmentos de bosque mesófilo en la región central de Veracruz y sugiere el uso de las plantaciones de café para conectar fragmentos de bosque como una alternativa para mantener las poblaciones de Sturnira ludovici y posiblemente otros frugívoros voladores.

Habitat heterogeneity is a primary ecological factor that is particularly pronounced in arid ecosystems. The Tehuacán valley is a subtropical semi-arid ecosystem in which several species of columnar cacti and agave (i.e., CAM plants) constitute the dominant elements accompanied by patches of trees and shrubs (i.e., C₃ plants). Vegetation in Tehuacán is isotopically heterogenous because CAM plants have less depleted δ¹³C values than C₃ plants. Fruits and flowers of cactus and agaves offer abundant food to vertebrates, but their leaves might be less attractive to insects than the leaves of C₃ plants. Therefore, we use carbon and nitrogen stable isotope analysis to test the hypothesis that C₃ and CAM food would contribute asymmetrically to different guilds of birds and bats. We predict that granivorous and frugivorous birds and nectarivorous and frugivorous bats will consume a CAM diet, whereas insectivorous birds and bats will consume a C₃ diet. Due to omnivory of bird and bat consumers, we predict that the importance of CAM food will decrease as the trophic level of the animal increases. Our results showed that CAM food predominated in plant-eating birds and in some flower-visiting bats, whereas C₃ food predominated in insect-eating bats and birds and frugivorous bats. Habitat heterogeneity in Tehuacán is important for conservation due to the asymmetric role of CAM and C₃ food in the nutrition of different feeding guilds of vertebrates. Our study provides basic information to evaluate the potential impact of habitat loss on functional groups of consumers in a semi-arid ecosystem.

La heterogeneidad del hábitat es un factor ecológico primario que es particularmente pronunciado en los ecosistemas áridos. El valle de Tehuacán es un ecosistema subtropical semiárido en el que varias especies de cactáceas columnares y agaves (e.g., plantas MAC) constituyen los elementos dominantes acompañados por grupos de árboles y arbustos (e.g., plantas C₃). La vegetación en Tehuacán es isotópicamente heterogénea ya que las plantas MAC tienen valores de δ¹³C menos negativos que las plantas C₃. Las frutas y las flores de cactus y agaves ofrecen comida abundante a los vertebrados, pero sus hojas podrían ser menos atractivas para los insectos que las hojas de las plantas C₃. Por lo tanto, utilizamos análisis de isótopos estables de carbono y nitrógeno para probar la hipótesis de que los alimentos C₃ y MAC contribuyen asimétricamente a los gremios de aves y murciélagos. Predecimos que las aves granívoras y frugívoras, y los murciélagos frugívoros y nectarívoros consumirán una dieta MAC, mientras que las aves y murciélagos insectívoros consumirán una dieta C₃. Debido a la omnivoría de aves y murciélagos, predecimos que la importancia del alimento MAC disminuirá a medida que el nivel trófico de los animales aumente. Nuestros resultados mostraron que el alimento MAC predominó en aves herbívoras y en algunos murciélagos nectarívoros, mientras que el alimento C₃ predominó en los murciélagos y aves que se alimentan insectos y en los murciélagos frugívoros. La heterogeneidad del hábitat en Tehuacán es importante para la conservación debido al papel asimétrico de los alimentos MAC y C₃ en la nutrición de los diferentes gremios alimentarios de vertebrados. Nuestro estudio proporciona información básica para evaluar el posible impacto de la pérdida de hábitat en los grupos funcionales de los consumidores en un ecosistema semiárido.

In the Peruvian Amazon, white-sand forests are patchily distributed and restricted to a few localities in the North. Although recent studies have documented patterns of habitat specialization by plants in these unique forests, very few studies of the fauna of these habitats have been conducted. The species composition of the avifauna of the white-sand forests at six localities in the region was sampled by conducting transects and point counts. Surrounding habitats were also sampled to compare avifaunal communities and to determine the degree of restriction of bird species to white-sand habitats. Non-metric multidimensional scaling analysis showed that bird communities of white-sand forests were more similar to each other than they were to terra firme or flooded forest communities. Sites on either side of the Amazon-Marañón barrier were the most similar within habitat type consistent with the hypothesis that these rivers represent a major biogeographic barrier. Twenty-six species, belonging to 13 families, were to some degree specialized to white-sand forests. This is the first comprehensive ornithological assessment carried out on these habitats in Peru. The high degree of habitat specialization found in these 26 bird species highlights the need for conservation and management measures that will protect white-sand forests.

Los bosques sobre arena blanca están distribuidos en parches y restringidos a unas pocas localidades en el Norte de la Amazonía peruana. Aunque estudios recientes han documentado patrones de especialización por hábitat de las plantas en estos bosques únicos, existen muy pocos estudios sobre la fauna. La composición de especies de la avifauna de los bosques sobre arena blanca fue estudiada en seis localidades por medio de transectos y conteos de puntos. Los hábitats circundantes también fueron evaluados para comparar las comunidades de aves y para determinar el grado de restricción de las especies de aves a los hábitats de arena blanca. El análisis de escala multidimensional no-métrica mostró que las comunidades de aves de los bosques sobre arena blanca fueron más similares entre sí que con las comunidades de tierra firme o de los bosques inundables. Las localidades a cada lado de la barrera del Amazonas-Marañón fueron más similares dentro de cada tipo de hábitat, consistente con la hipótesis de que esos ríos representan una barrera biogeográfica importante. Veintiséis especies, pertenecientes a trece familias, estuvieron especializadas en algún grado en los bosques sobre arena blanca. Esta es la primera evaluación ornitológica comprehensiva llevada a cabo en estos hábitats en Perú. El alto grado de especialización por hábitat encontrado en estas 26 especies de aves resalta la necesidad de medidas de conservación y manejo para proteger los bosques sobre arena blanca.

Jaguars (Panthera onca) and pumas (Puma concolor) coexist throughout the Neotropics. Using camera trapping in four Brazilian biomes, we compare the daily activity patterns of the jaguar and puma, and their relationships with their main prey species. We used a kernel density method to quantify daily activity patterns and to investigate overlap between these predators and their main prey. Both cats showed intensive nocturnal and crepuscular activity (0.69 and 0.14 kernel density, respectively, for jaguars; 0.68 and 0.19 kernel density, respectively, for pumas). Only in the Pantanal did we observe a pattern of concentrated diurnal activity for both species. We found little temporal segregation between jaguars and pumas, as they showed similar activity patterns with high coefficients of overlapping (average ∆₁ = 0.86; SE = 0.15). We also observed a significant overlap between the activity patterns of the predators and their main prey species, suggesting that both predators adjust their activity to reduce their foraging energy expenditure. Our findings suggest that temporal partitioning is probably not a generalized mechanism of coexistence between jaguars and pumas; instead, the partitioning of habitat/space use and food resources may play a larger role in mediating top predator coexistence. Knowledge about these behavior aspects is crucial to elucidating the factors that enable coexistence of jaguars and pumas. Furthermore, an understanding of their respective activity periods is relevant to management and associated research efforts.

Onças-pintadas (Panthera onca) e onças-pardas coexistem em todo o Neotrópico. Embora existam vários estudos sobre a coexistência dessas duas espécies, somente alguns investigam o padrão de atividade temporal entre biomas. Usando armadilhas fotográficas em quatro biomas Brasileiros comparamos o padrão de atividade diário de pintadas e pardas, e a relação com suas principais espécies presa. Usamos o método de densidade Kernel para quantificar o padrão de atividade diária e investigar a sobreposição entre estes predadores e suas principais presas. As duas espécies apresentam uma intensa atividade noturna e crepuscular (0.69 e 0.14 de densidade kernel, respectivamente para pintadas; 0.68 e 0.19 de densidade kernel, respectivamente para pardas). Somente no Pantanal observamos um maior patrão de atividade diurno para ambas as espécies. Verificamos pouca segregação temporal entre onças pintadas e pardas, uma vez que demonstraram similar atividade com altos coeficientes de sobreposição (média ∆₁ = 0.86; SE = 0.15). Também observamos uma significante sobreposição entre o padrão de atividade destes predadores e suas principais espécies presa, sugerindo que ambos ajustam suas atividades para reduzir o gasto energético no forrageamento. Nossos resultados sugerem que provavelmente o particionamento temporal não é um mecanismo generalizado de coexistência entre onças pintadas e pardas; em alternativa a segregação do uso do habitat/espaço e de recursos alimentares podem desempenhar um papel mais importante na mediação da coexistência entre esses predadores topo nessas áreas. O conhecimento sobre estes aspectos comportamentais é fundamental para elucidar os fatores que permitem a coexistência entre onças-pintadas e onças-pardas. Por fim, compreender o padrão de atividade das espécies é relevante para sua gestão e esforços de pesquisa.

Resource availability can influence animal movement causing changes in home-range size and arrangement between seasons. We investigated the influence of acuri palm (Attalea phalerata) on the occupancy of agouti Dasyprocta azare during both the dry and rainy seasons, as well as the abandonment probabilities in the transition between seasons in the Brazilian Pantanal. The agoutis occupied a high proportion of the forested areas in the rainy season (0.83), but the occupancy decreased in the dry season (0.39). In the rainy season, occupancy by agoutis was not correlated with acuri palm availability, while in the dry season, it was positively correlated with the palm's availability. The acuri palm availability also drove the agoutis' probability of site abandonment from the rainy to the dry season, with higher abandonment probability in sites with low acuri palm availability. These findings show that this large-seeded palm can be an important resource for the agoutis' populations during the fruit-scarcity period. The acuri palm seeds may be particularly important for agoutis using fragmented forests, given that the large-seeded palms are able to persist even in small fragments, which is untrue for other important resource.

A disponibilidade de alimentos pode influenciar a movimentação animal causando mudanças no tamanho das áreas de vida dos indivíduos e em seu arranjo entre estações. Nós investigamos a influência da palmeira acuri (Attalea phalerata) na ocupação da cutia Dasyprocta azarae durante as estações chuvosa e seca, assim como nas probabilidades de abandono na transição entre essas duas estações no Pantanal brasileiro. As cutias ocuparam uma alta proporção das áreas florestadas na estação chuvosa (0,83), mas a ocupação diminuiu na estação seca (0,39). Na estação chuvosa, a ocupação das cutias não foi correlacionada com a disponibilidade de acuri, enquanto na estação seca foi positivamente correlacionada com a disponibilidade da palmeira. A disponibilidade do acuri também conduziu a probabilidade de abandono das cutias da estação chuvosa para a estação seca, com uma maior probabilidade de abandono em locais com baixa disponibilidade de acuri. Esses resultados mostram que palmeiras de sementes grandes podem ser um importante recurso para as populações de cutias durante o período de escassez de frutos. Os frutos do acuri podem ser particularmente importantes para cutias que habitam florestas fragmentadas, levando-se em consideração que algumas populações de palmeiras de sementes grandes podem persistir em fragmentos pequenos, o que não é verdade para outros recursos importantes.

Whether aging forest fragments are able to recover original assemblages or progressively move toward impoverished successional stages remains as an open question. This study tested the hypothesis that seedling assemblages in forest fragments differ from those across mature forest stands and examined to what extent the uncovered patterns supported the notion that edge-affected habitats tend to support impoverished tree assemblages dominated by pioneer species. We contrasted a series of small forest remnants (3–91 ha) to old-growth stands located in the largest (ca 3500 ha) and best preserved forest remnant in northeastern Brazil and found that tree seedling assemblages inhabiting forest fragments exhibited reduced species richness (up to 50%) at different spatial scales in comparison to seedling assemblages in mature forest and adult assemblages in both fragments and mature forest stands. Moreover, ordination analyses clearly segregated fragment seedling assemblages in taxonomic/functional terms and segregation correlated to the richness of pioneer species. Seedlings of pioneer species and those bearing medium-sized seeds (0.6–1.5 cm) increased in fragments, whereas large-seeded species (1.5–3.0 cm) were reduced by more than a half. Such a multiple-scale replacement of the old-growth flora by pioneers was also confirmed by an indicator species analysis and the resulting pioneer indicator species. Our results suggest that small forest fragments support impoverished and distorted seedling assemblages. This floristic/functional drift implies that forest remnants or edge-affected habitats tend to be dominated by a small set of pioneer tree species rather than supporting a substantial portion of the old-growth flora as do mature forest stands.

Se os fragmentos florestais são capazes de naturalmente restaurar as assembleias originais ou tendem a suportar apenas assembleias sucessionais empobrecidas permanece uma questão aberta. Neste estudo nós examinamos a hipótese que as assembleias de plântulas em fragmentos florestais diferem daquelas em áreas de floresta madura e analisamos em que medida os padrões encontrados suportam a ideia que habitats afetados pelos efeitos de borda tendem a apresentar assembleias de árvores empobrecidas e dominadas por espécies pioneiras. Nós comparamos uma série de pequenos fragmentos florestais (3–91 ha) com áreas de floresta madura localizadas no maior remanescente de floresta Atlântica no nordeste do Brasil (ca. 3500 ha). As assembleias de plântulas de espécies arbóreas nos pequenos fragmentos apresentaram uma redução na riqueza de espécies (até 50%) em diferentes escalas espaciais em comparação com as assembleias de plântulas em áreas de floresta madura e as assembleias de árvores adultas nos pequenos fragmentos e áreas de floresta madura. Plântulas de espécies pioneiras e com sementes de tamanho médio (0.6–1.5 cm) apresentaram um aumento na riqueza relativa nos pequenos fragmentos, enquanto espécies com grandes sementes (>1.5–3.0 cm) apresentaram uma redução maior que 50 por cento. Análises de ordenamento e de espécies indicadoras também revelaram a substituição da flora típica de floresta madura por plantas pioneiras nos pequenos fragmentos. Nossos resultados sugerem que pequenos fragmentos florestais suportam uma flora de plântulas empobrecida. Essa deriva florística/funcional implica que os remanescentes florestais ou habitats afetados pelos efeitos de borda tendem a ser dominados por um pequeno grupo de árvores pioneiras ao invés de suportarem uma parte substancial da flora típica de floresta madura.

Tropical dry forests are the most threatened forest type in the world yet a paucity of research about them stymies development of appropriate conservation actions. The Paranã River Basin has the most significant dry forest formations in the Cerrado biome of central Brazil and is threatened by intense land conversion to pastures and agriculture. We examined changes in Paranã River Basin deforestation rates and fragmentation across three time intervals that covered 31 yr using Landsat imagery. Our results indicated a 66.3 percent decrease in forest extent between 1977 and 2008, with an annual rate of forest cover change of 3.5 percent. Landscape metrics further indicated severe forest loss and fragmentation, resulting in an increase in the number of fragments and reduction in patch sizes. Forest fragments in flatlands have virtually disappeared and the only significant forest remnants are mostly found over limestone outcrops in the eastern part of the basin. If current patterns persist, we project that these forests will likely disappear within 25 yr. These patterns may be reversed with creation of protected areas and involvement of local people to preserve small fragments that can be managed for restoration.

As florestas tropicais secas são as mais ameaçadas do mundo e a escassez de estudos sobre estes ecossistemas dificulta o desenvolvimento de ações de conservação adequadas. A bacia do Rio Paranã possui a mais importante formação florestal seca do bioma Cerrado no Brasil central e está ameaçada pela intensa conversão de terras para pastagens e agricultura. Neste estudo avaliamos mudanças nas taxas de desmatamento e fragmentação destas florestas secas em três intervalos de tempo ao longo de 31 anos, usando imagens Landsat. Nossos resultados indicaram uma diminuição de 66,3% na extensão das florestas secas entre 1977 e 2008, com uma taxa anual de mudança da cobertura florestal de 3,5%. Métricas de paisagem indicaram ainda perdas significantes de área florestal e severa fragmentação, resultando num aumento do número de fragmentos e na redução do tamanho de manchas de floresta. Os fragmentos florestais em áreas planas praticamente desapareceram e os únicos remanescentes florestais significativos são encontrados principalmente sobre afloramentos calcários na parte leste da bacia. Se os padrões atuais de desmatamento persistirem, estimamos que essas florestas provavelmente desapareçam dentro de 25 anos. Esses padrões podem ser revertidos com a criação de áreas protegidas e com o envolvimento da população local em busca da preservação de pequenos fragmentos, manejados para a restauração.

Accelerated human development in coastal areas is causing declines in coral reefs worldwide, but the mechanisms by which development leads to reef degradation are often difficult to identify. Here, we use Akaike information criterion model averaging in combination with path analysis to test for the direct and indirect effects of potential environmental stressors on two coral diseases on the west coast of Hawai'i. We quantified human-altered land cover and human population density at two spatial scales: inland area of 1-km radius and watershed. We then tested for the effects of these land cover variables, as well as seawater chlorophyll α concentrations, depth, host coral cover, and proximity to surface water discharge on the density of growth anomalies (GA) and prevalence of trematodiasis (TRE) affecting Porites lobata, the locally dominant reef-building coral species. Our analyses showed that human-altered land cover measured at 1-km scale was a strong indirect predictor of GA. Specifically, we found that human interference adjacent to the coast predicted higher chlorophyll α concentrations, which in turn predicted higher GA density. We also found that chlorophyll α and depth were strong negative predictors of TRE, and host coral cover a positive predictor. Our results indicated that GA are likely regulated by indirect land-based anthropogenic impacts, whereas TRE is mostly affected by host density-dependent forces. Path analysis can serve as a useful tool to rapidly identify the scale and indirect effects of anthropogenic stressors related to coral diseases, allowing for accurate conservation planning in the face of limited resources for tropical conservation.