1. Tropical montane amphibians have been the focus of recent and crucial conservation efforts. These initiatives require understanding on how elevation influences amphibian body temperature beyond the simplistic assumption of a monotonical decrease with elevation. This study addresses patterns and potential for inference in this context.

2. As elevation increases, mean body temperature (BT) of tropical montane amphibians decreases linearly, but intrapopulation variation (VAR) in BT increases exponentially. These relationships are influenced by biome structure, but display both local nuances and species-specific remarks.

3. Substrate temperature (ST) and BT hold a close relationship across elevation. The noise around this relationship is lowest in mid-elevation cloud forests and maximum in the paramo, a biome above the tree line.

4. The relationships between BT and ST, and between elevation and either BT or VAR, are valuable to infer general patterns of thermal ecology for amphibians and to highlight species-specific exceptional cases.

5. The BT of montane tropical amphibians can be estimated from temperature data collected at a scale compatible with the size and microhabitat of individual frogs. Estimates from elevation are valid as general trends that can be enhanced if natural history is taken into account. Worldclim data allow for rough inference only and have limited predictive power.

6. A framework is proposed to study how the BT and VAR of amphibians change with elevation. This framework encompasses information on biome structure and natural history.

1. Parasitoid acceptance of host individuals that differ in suitability is dynamic, varying with physiological state and experience. Female parasitoids with high egg loads and low life expectancy (i.e. time limited) are more willing to accept hosts with low suitability for progeny development than females with low egg loads and high life expectancy (i.e. egg limited). However, studies of dynamic acceptance behaviour in parasitoids have only considered high- vs. low-suitability host individuals within the same host species.
2. Here, we report the first results on whether acceptance of individuals from different host species that vary in suitability is also dynamic, using two aphid parasitoid species in the genus Aphelinus (Hymenoptera: Aphelinidae).
3. Stressors (starvation and age) and experience that increase time limitation did not affect the acceptance of low-suitability host species by two Aphelinus species with reciprocal specificities.
4. Oviposition in a high-suitability host species increased with egg load, but did not vary with egg load for females exposed to low-suitability host species. This is an unexpected pattern since it results in proportionally higher acceptance of low-suitability hosts with decreasing egg load.
5. The stability of behavioural host specificity in these parasitoids under very stressful conditions might be explained by (i) frequent transient egg limitation, (ii) higher fitness from egg resorption than oviposition or (iii) neural constraints on host recognition.
6. If neural constraints restrict the ability of these specialists to change their behaviour under stress, we predict that generalist species of Aphelinus should show greater dynamism in acceptance of low-suitability hosts. We are testing this prediction using Aphelinus species with very broad host ranges.

1. Native species might be able to persist in the face of a detrimental exotic invader by occupying refuge habitats where the exotic is not successful. These refuges might then provide demographic subsidies that enhance persistence of the native species in areas of coexistence with the exotic species. Phenotypic plasticity of the native species could play a critical role in this process by allowing individuals dispersing from refuge to invaded habitats to adaptively modify their phenotypes, thereby enhancing the subsidy. By contrast, locally adapted genetic or maternal differences between native populations could result in fitness disadvantages for dispersers at invaded habitats, thereby reducing the subsidy.
2. We studied phenotypic variation in a native amphipod (Gammarus fasciatus) across ion gradients in Lac St. Louis, Québec, Canada. Ion gradients determine refuge vs. invaded habitats because native amphipods are found in both ion-poor and ion-rich habitats, whereas exotic (Echinogammarus ischnus) amphipods are found only in the latter.
3. We tested for plastic vs. genetic/maternal contributions to spatial variation (ion-rich vs. ion-poor habitats) in native amphipod fitness components: postmoult calcification, body size, larval survival, time to first reproduction and fecundity. We did so by comparing the following: (i) F₀ (collected from the wild) individuals between the two habitats – some of which were reared for a time under varying conditions in the laboratory; and (ii) F₁ (reared in the laboratory for their entire lives) individuals from the two habitats under a variety of water conditions.
4. We found strong plastic effects on postmoult calcification – it was more rapid in ion-rich water. We found genetic/maternal differences in time to reproduction (almost twice as long in ion-poor amphipods), fecundity and larval survival (higher in ion-poor amphipods) in early summer. These plastic effects and genetic/maternal differences are likely to be adaptive.
5. Plasticity and genetic/maternal effects both could influence the efficacy of ion-poor populations in providing demographic subsidies that aid native persistence at ion-rich habitats where exotic amphipods are present. These effects could thus have important consequences for native species persistence in the presence of non-native species.

1. Frugivory among bats (Chiroptera) has evolved independently in the New and Old World tropics: within the families Phyllostomidae and Pteropodidae, respectively. Bats from both families rely primarily on olfaction for the location of fruits. However, the influence of bats on the evolution of fruit scent is almost completely unknown.
2. Using the genus Ficus as a model, the aims of this study were to explore the chemical composition of fruit scent in relation to two contrasting seed dispersal syndromes in Panama and Malaysia and to assess the influence of fruit scent on the foraging behaviour of neo- and palaeotropical fruit-eating bats (Artibeus jamaicensis and Cynopterus brachyotis, respectively). Two hypotheses were tested: (i) variation in fruit scent, between bat- and bird-dispersed figs, is independent of phylogeny and (ii) Old and New World fruit bats, which have evolved independently in each hemisphere, share the same olfactory preferences with respect to fruit scent.
3. The fruit scents of bat- and bird-dispersed fig species were sampled in the field, using dynamic headspace adsorption techniques. New and Old World fruit bats were then captured and tested on natural fig fruit scents from both hemispheres.
4. Chemical analyses, using gas chromatography (GC) and GC/mass spectrometry (MS), revealed a broad overlap in scent compounds between bat-dispersed fig species from both hemispheres. Their fruit scents were dominated by monoterpenes, which contrary to phylogenetic predictions, were completely absent from bird-dispersed species from both regions.
5. The fruit scents of bat-dispersed figs were highly attractive to neotropical bats (A. jamaicensis) in behavioural experiments, whereas those of bird-dispersed figs were completely rejected. Neotropical bats (A. jamaicensis) exhibited a significant preference for fig fruit scents dominated by monoterpenes, independent of the geographical origin of the scent. Palaeotropical bats (C. brachyotis), by contrast, rejected monoterpene-rich fruit scents from the Neotropics.
6. In a cluster analysis (which included additional, published data from the literature), the fruit scents of bat-dispersed figs were clumped by subgenus, with the exception of palaeotropical figs of the subgenus Sycomorus. C. brachyotis, from Malaysia, was the only fruit bat species that significantly preferred the fruit scents of Sycomorus figs that contained no monoterpenes.

1. Exaggeration of male sexual ornaments should be costly, in terms of metabolic expenditure, resource allocation or even locomotor function. For example, many male ornaments are predicted to affect the aerodynamics, drag or biomechanics of movement and thus inhibit the speed or manoeuvrability of individuals; but empirical support for this is equivocal.
2. We tested the locomotor and metabolic costs of exaggerated male ornaments in the threadfin rainbowfish (Iriatherina werneri), an Australasian native fish characterized by excessively long fin streamers. We predicted that males with greater relative ornamentation would have reduced escape abilities (i.e. burst swim speeds) as well as higher metabolic costs when resting or swimming. Furthermore, we evaluated the benefits of the signal by comparing the preference of females for males with differing amounts of ornamentation.
3. As expected, we found that females spent more time observing (i.e. preferred) males with longer relative fins. We also experimentally reduced threadfin length and found that females continued to show preference for males with longer fins, rather than a preference for particular males.
4. Male I. werneri with longer ornaments had higher resting metabolic rates, but we found no effect of ornament size on metabolic rates during swimming. Males with longer threadfins tended to swim faster, but our manipulation of fin length had no effect on burst swimming speed, indicating swimming abilities are not causally related to threadfin length.
5. Overall, we found no evidence that the extravagant ornaments of male threadfin rainbowfish increase the metabolic or functional costs associated with swimming. Our results are surprising, given the high viscosity of water and the extreme length of I. werneri's ornaments. We suggest that future work should focus on the fitness costs of threadfin length, relative to reproductive output or survival under more natural conditions.

1. Herbivores can have contrasted impacts on litter quality and litter decomposition, through an alteration of leaf chemistry and leaf senescence. Depending on the context, herbivores can induce defensive secondary compounds and thus slow down litter decomposition or accelerate decomposition by short-cutting nutrient resorption.
2. Almost nothing is known for grasses, which contain smaller amounts of secondary compounds than forbs and trees. Because grasses span a gradient from exploitative species having a low C : N ratio and induced defences, to conservative species having a high C : N ratio and constitutive defences, we hypothesize that the litter dynamics of functionally contrasted grasses may be differentially altered by herbivores.
3. In a mesocosm experiment, we assessed the litter decomposition rate of two subalpine grasses, the more exploitative Dactylis glomerata and the conservative Festuca paniculata, in the presence of two grasshopper species, Chorthippus scalaris and Euthystira brachyptera. We hypothesized that decomposition patterns depending on grass species and herbivory could be explained by the C : N ratio and the total phenolic content of fresh, senescent and decomposed leaves.
4. Herbivory by grasshoppers induced the accumulation of phenolics in the fresh leaves of D. glomerata, but most of these compounds were lost during senescence. The decomposition rate of D. glomerata senescent leaves did not depend on herbivory, phenolics and N content or C : N ratio. In contrast, herbivory did not induce any phenolic accumulation in the grazed leaves of F. paniculata, but during senescence, phenolics disappeared in greater proportions in grazed leaves than in ungrazed leaves, probably due to the physical alteration of grazed leaves. Herbivory slowed down the decomposition rate of F. paniculata, which was correlated to the phenolic concentration of senescent leaves, but not to the C : N ratio or N content.
5. Herbivory by grasshoppers differentially altered the litter decomposition rate of the two functionally contrasted grasses, having no effect on D. glomerata and slowing down F. paniculata. Thus, the combination of chemical and physical modifications of leaves by grazing and their interaction with grass traits may have either accelerating or decelerating effects on litter decomposition, with potentially complex outcomes at the ecosystem level.

1. In all stages of their life cycle, insects are threatened by a multitude of predators, parasites, parasitoids and pathogens. The lifestyles and feeding ecologies of some hymenopteran taxa render them especially vulnerable to pathogen infestation. Specifically, development in sub-terranean brood cells, mass provisioning of resources for the offspring and the life of social insects in large communities can enhance the risk of pathogen infestation and/or the spread of disease among conspecifics.
2. To counteract these threats, insects have evolved mechanical, chemical and behavioural defences as well as a complex immune system. In addition to the host's own defences, some Hymenoptera are associated with protective symbionts. Leaf-cutting ants, solitary digger wasps, bees and bumblebees engage in symbiotic interactions with bacteria that protect the adult host, the developing offspring or the food resources against microbial infections. In the well-studied cases of ants and wasps, the protective activity is mediated by the production of antimicrobial secondary metabolites. In other symbiotic interactions, however, competitive exclusion and immune priming may also play an important role in enhancing protection. Phylogenetic studies indicate that the defensive associations in Hymenoptera are generally more dynamic than the intimate nutritional mutualisms, with horizontal transfer or de novo uptake of the symbionts from the environment occurring frequently.
3. Mutualistic micro-organisms can also significantly influence the outcome of host-parasitoid interactions. Some insects are protected by symbiont-produced toxins against parasitic wasps. Ichneumonid and braconid parasitoids, on the other hand, are associated with symbiotic viruses that are injected into the caterpillar host during oviposition and suppress its immune system to the advantage of the parasitoid.
4. The increasing affordability of next-generation sequencing technologies will greatly facilitate the analysis of insect-associated microbial communities and undoubtedly uncover a plethora of as yet unknown protective symbioses. However, a detailed understanding of the host's natural history is indispensable for elucidating the fitness benefits of the symbionts and the molecular basis of symbiont-conferred protection.

1. Genetic background, prenatal and post-natal early-life conditions influence the development of interconnected physiological systems and thereby shape the phenotype. Certain combinations of genotypes and pre- and post-natal conditions may provide higher fitness in a specific environmental context.
2. Here, we investigated how grey partridges Perdix perdix of two strains (wild and domesticated) cope physiologically with pre- and post-natal predictable vs. unpredictable food supply. Food unpredictability occurs frequently in wild environments and requires physiological and behavioural adjustments.
3. Well-orchestrated and efficient physiological systems are presumably more vital in a wild environment as compared to captivity. We thus predicted that wild-strain grey partridges have a stronger immunity, glucocorticoid (GC) stress response and oxidative stress resistance (OSR) than domesticated birds, which have undergone adaptations to captivity. We also predicted that wild-strain birds react more strongly to environmental stimuli and, when faced with harsh prenatal conditions, are better able to prepare their offspring for similarly poor post-natal conditions than birds of domesticated origin.
4. We found that wild-strain offspring were physiologically better prepared for stressful situations as compared to the domesticated strain. They had a high GC stress response and a high OSR when kept under predictable food supply. Wild-strain parents reacted to prenatal unpredictable food supply by lowering their offspring's GC stress response, which potentially lowered GC-induced oxidative pressure. No such pattern was evident in the domesticated birds.
5. Irrespective of strain and prenatal feeding scheme, post-natal unpredictable food supply boosted immune indices, and GC stress response was negatively related to antibody response in females and to mitochondrial superoxide production.
6. Wild-strain grey partridge showed fitness-relevant physiological advantages and appeared to prepare their offspring for the prospective environment. Negative relationships between GC stress response, immunity and oxidative indices imply a pivotal role of an organism's oxidative balance and support the importance of considering multiple physiological systems simultaneously.

1. Accumulating evidence suggests that the average body size of many organisms is declining in response to climate warming. This phenomenon has been suggested to represent a universal response to warming that may impose significant adverse effects on ecosystem functioning and services.
2. However, we do not have a thorough understanding of why body sizes are commonly declining, and why some organisms show the opposite response. Because ectotherms constitute the vast majority of organism biomass and about 99% of species worldwide, it is particularly important to understand how ectotherms respond to a warming climate.
3. This review discusses the underlying physiological mechanisms of changes in ectotherm body size and addresses observed responses within a broad ecological context at different levels of organization, from individuals to communities, particularly in aquatic systems.
4. Warming-induced responses in average body size are not only determined by changes in rates of individual growth and development, but also mediated through size-dependent feedbacks at the population level, as well as competitive and predatory interactions within the community. Emergent properties at higher organizational levels have already been observed in both experimental and natural systems.
5. Various approaches will be required for enhancing our knowledge about the importance of such processes in natural systems. These include controlled semi-natural experiments and phylogenetic comparisons as well as statistical models of time-series data and theoretical models linking climate effects at the individual, population and community levels.
6. Understanding causes of observed changes in organism body sizes and how these depend on the ecological context is essential for improving our predictions and the management of ecosystems in the face of a warming climate.

1. Three main directions of adaptive specialization are evident in the world flora, reflecting fundamental trade-offs between economics (conservative vs. acquisitive investment of resources) and size. The current method of ordinating plants according to these trade-offs, CSR classification, cannot be applied to the woody species that dominate many terrestrial ecosystems.
2. We aimed to produce a novel CSR classification method applicable to vascular plants in general.
3. Principal components analysis (PCA) of variation in a range of plant traits for 678 angiosperm, gymnosperm and pteridophyte species was used to determine the limits to multivariate space occupied by functionally diverse species. From this calibration, correlations between PCA axes and values of leaf dry matter content (LDMC; as an index of conservatism in life history), specific leaf area (SLA; indicative of acquisitive economics) and leaf area (LA; photosynthetic organ size) were used to produce predictor regressions from which target species could be compared against the multivariate space. A spreadsheet was developed that returned ternary coordinates and tertiary CSR strategies for target subjects based on LA, LDMC and SLA values.
4. The method allowed classification of target species within a triangular space corresponding to Grime's theoretical CSR triangle and was sufficiently precise to distinguish strategies between species within genera and within populations of species. It was also largely in agreement with previous methods of CSR classification for herbaceous species.
5. Rapid CSR classification of woody and herbaceous vascular plants is now possible, potentially allowing primary plant functional types and ecosystem processes to be investigated over landscape scales.

1. Ability to self-fertilize is correlated with invasiveness in several introduced floras, and this has been attributed to its mitigating effect on fecundity when pollinator visitation and mate availability are inadequate. Cross-pollination opportunities are expected to be most limited in isolated individuals and small populations, both typical of the leading edge of an invasion. Thus, self-pollination may promote invasion in part by mitigating pollen-limitation Allee effects.

2. We used emasculation and pollen supplementation experiments to test whether the importance of self-pollination for fecundity increased as plant abundance decreased and isolation increased, in the hawkmoth-pollinated and autonomously self-pollinating invasive lily Lilium formosanum, in its introduced range in KwaZulu-Natal, South Africa. As inbreeding depression is negligible in these populations, seed production through selfing is likely to be demographically important.

3. In naturalized populations of L. formosanum, varying in size and degree of isolation, emasculation reduced seed production by two-thirds, indicating strong reliance on self-fertilization for fecundity due to inadequate pollinator visitation. However, this was not related to population size and was only greater for more isolated populations in one of the 3 years in which the experiment was carried out. Pollen supplementation experiments showed that pollen limitation was low – 12% on average – and significant in only one of 3 years, demonstrating that autonomous self-pollination was highly effective.

4. In artificial arrays, consisting of plants placed inside naturalized populations or in pairs isolated (3–702 m) from populations, the effect of emasculation on fecundity was greater in isolated plants than those inside the population in one of two populations. Isolation reduced fecundity when emasculated plants were placed next to a second emasculated plant, but not when emasculated plants were partnered with an intact plant, from which they could receive pollen.

5. We conclude that self-fertilization in L. formosanum compensates for inadequate pollinator visitation across all levels of population size and for a pollen-limitation Allee effect due to decreased mate availability in isolated plants, and may thus play an important role in invasion.

1. Plants form mutualistic symbioses with a variety of microorganisms including endophytic fungi that live inside the plant and cause no overt symptoms of infection. Some endophytic fungi form defensive mutualisms based on the production of bioactive metabolites that protect the plant from herbivores in exchange for a protected niche and nutrition from the host plant. Key elements of these symbioses are vertical transmission of the fungus through seed of the host plant, a narrow host range, and production of bioactive metabolites by the fungus.
2. Grasses frequently form symbioses with endophytic fungi belonging to the family Clavicipitaceae. These symbioses have been studied extensively because of their significant impacts on insect and mammalian herbivores. Many of the impacts are likely due to the production of four classes of bioactive alkaloids – ergot alkaloids, lolines, indole-diterpenes and peramine – that are distributed in different combinations among endophyte taxa.
3. Several legumes, including locoweeds, are associated with a toxic syndrome called locoism as a result of their accumulation of swainsonine. Species in two genera were recently found to contain previously undescribed endophytic fungi (Undifilum spp., family Pleosporaceae) that are the source of that toxin. The fungi are strictly vertically transmitted and have narrow host ranges.
4. Some plant species in the morning glory family (Convolvulaceae) also form symbioses with endophytic fungi of the Clavicipitaceae that produce ergot alkaloids and, perhaps in at least one case, lolines. Other species in this plant family form symbioses with undescribed fungi that produce swainsonine. The swainsonine-producing endophytes associated with the Convolvulaceae are distinct from the Undifilum spp. associated with locoweeds and the Clavicipitaceous fungi associated with Convolvulaceae.
5. In the establishment of vertically transmitted symbioses, fungi must have entered the symbiosis with traits that were immediately useful to the plant. Bioactive metabolites are likely candidates for such pre-adapted traits which were likely useful to the free-living fungi as well. With future research, vertically transmitted fungi from diverse clades with narrow host ranges and that produce bioactive compounds are likely to be found as important mutualists in additional plants.

1. Competition for resources has long been considered a prevalent force in structuring plant communities and natural selection, yet our understanding of the mechanisms that underlie resource competition is still developing.
2. The complexity of resource competition is derived not only from the variability of resource limitation in space and time and among species, but also from the complexity of the resources themselves. Nutrients, water and light each differ in their properties, which generates unique ways that plants compete for these resources.
3. Here, we discuss the roles of supply pre-emption and availability reduction in competition for the three resources when supplied evenly in space and time. Plants compete for nutrients by pre-empting nutrient supplies from coming into contact with neighbours, which requires maximizing root length. Although water is also a soil resource, competition for water is generally considered to occur by availability reduction, favouring plants that can withstand the lowest water potential. Because light is supplied from above plants, individuals that situate their leaves above those of neighbours benefit directly from increased photosynthetic rates and indirectly by reducing the growth of those neighbours via shade. In communities where juveniles recruit in the shade of adults, traits of the most competitive species are biased towards those that confer greater survivorship and growth at the juvenile stage, even if those traits come at the expense of adult performance.
4. Understanding the mechanisms of competition also reveals how competition has influenced the evolution of plant species. For example, nutrient competition has selected for plants to maintain higher root length and light competition plants that are taller, with deeper, flatter canopies than would be optimal in the absence of competition.
5. In all, while more research is needed on competition for heterogeneous resource supplies as well as for water, understanding the mechanisms of competition increases the predictability of interspecific interactions and reveals how competition has altered the evolution of plants.

1. Plant competition has been studied for decades. Yet, it is still an elusive concept that means different things to different people, is resistant to direct study and is shrouded in semantic and statistical complexity. We still lack basic information about many competitive mechanisms, processes and outcomes and their relationship to other ecological processes, and about how local interactions between individuals are propagated through communities. We suggest here that two critical issues have been overlooked in previous studies.
2. First, there is a need for direct measurements of the process of competition as opposed to indirect mechanisms of competitive outcomes. Biomass has become the ‘industry standard’ for measuring competition, but we suggest that biomass cannot provide unambiguous insights into plant competition because it is the product of too great a range of factors and processes.
3. Second, the use of a single measure of competition at an arbitrarily assigned end point of an experiment misses much of the complexity of dynamic interactions between competing plants and can lead to erroneous interpretations. Here, we suggest approaches to handle these difficulties, using new techniques or the application of well-known methods in a novel way. We also provide examples of systems or questions where the improved understanding these approaches could bring would be of particular benefit.
4. Ultimately, we suggest the need for a major shift in the way in which we consider and measure plant competition to identify broadly agreed rules for variation in its importance, its role in different communities and habitats, and how and whether it influences or drives patterns of species diversity and abundance.

1. Reproductive efficiency (the efficiency of conversion of resources from vegetative tissue to reproductive output) is a central to our understanding of reproductive allocation and the evolution of reproductive strategies in plants. Plant strategy theory predicts that reproductive efficiency should decrease under competition. Short-lived semelparous species are not predicted to evolve under competition and therefore should not express adaptive responses to the presence of competitors. Long-lived iteroparous species are predicted to delay reproduction in favour of growth and resource acquisition in the presence of competitors. I use life-history theory to advance a prediction that reproductive efficiency increases under competition in both short-lived semelparous and potentially longer-lived iteroparous species.
2. Contrary to the predictions of plant strategy theory, short-lived semelparous species are frequently observed to live in highly competitive environments. Further, iteroparous species under intense competition may die long before they reach competitive dominance or an optimal size for reproduction.
3. I surveyed the literature for studies on plant species including measurements of vegetative and reproductive allocation in high and low (or no) competition treatments.
4. Across species, relative reproductive efficiency (reproductive efficiency under high competition/reproductive efficiency under low competition) significantly increased with increasing competition intensity.
5. Patterns of allocation to reproduction under competition support the existence of a competitive annual strategy and a reproductive perennial strategy. Under these strategies, short-lived semelparous species and long-lived iteroparous species express high reproductive efficiency under competition as an adaptation to high neighbour density. In addition, some species also expressed patterns of allocation to reproduction consistent with plant strategy theories.
6. Under this interpretation, I predict that competitive strategies, where plants delay reproduction in competitive environments to gain competitive superiority, are favoured not under intense competition but under modest competition. Including a life-history interpretation in reproductive efficiency under competition provides a much needed predictive framework for strategies of reproduction observed across species.

1. Models of the regulatory behaviour of organisms are fundamental to a strong physiologically-based understanding of species' responses to global environmental change. Biophysical models of heat and water exchange in organisms (biophysical ecology) and nutritionally-explicit models for understanding feeding behaviour and its fitness consequences (the Geometric Framework of nutrition, GF) are providing such an underpinning. However, temperature, water and nutrition interact in fundamental ways in influencing the responses of the organism to their environment, and a priority is to develop an integrated approach for conceptualising and measuring these interactions.
2. Ideally, such an approach would be based on a thermodynamically-formalized energy and mass budgeting approach that is sparsely parameterised and sufficiently general to apply across a range of situations and organisms. Here we illustrate how mass-balance aspects of Dynamic Energy Budget theory can be applied to obtain first-principles estimates of fluxes of O₂, CO₂, H₂O and nitrogenous waste.
3. Then, using an herbivorous lizard (Egernia cunninghami) as a case study, we demonstrate how these estimates can be integrated with heat/water exchange models and environmental data to provide a holistic understanding of how foraging strategy, food availability, habitat and weather interact with heat, water and nutrient/energy budgets across the life-cycle.
4. The analysis shows the potential importance of the water balance in affecting the energy budgets of ‘ dry skinned’ ectotherms, especially early in ontogeny, and highlights a significant gap in our knowledge of the physiological and behavioural traits that affect water balance when compared with our knowledge of thermal traits.
5. In general, the modelling approach we describe can provide the thermodynamically-constrained stage on which other evolutionary and ecological interactions play out; the ‘thermodynamic niche’. This in turn provides a solid foundation from which to tackle key questions about organismal responses to environmental change.

1. Our ability to generalize about broad patterns and outcomes of competitive interactions among plants has improved from a better understanding of functional traits. Facilitative interactions among plants also exhibit strong trait-based patterns; however, very little empirical research has addressed the trait basis of different facilitative mechanisms or the applicability of traditionally defined functional strategies to facilitation.
2. We present a series of predictions regarding the trait basis of a variety of facilitative mechanisms based on empirical patterns of trait responses to environmental filters and knowledge of plant–environment feedbacks.
3. Using a leaf-height-seed framework to predict plant responses to facilitative effects of neighbours, we identify two categories of facilitative mechanisms based on similar predicted responses of specific leaf area (SLA), height and seed size: (i) facilitation of low-SLA, large-seeded and tall plants in environments typified by periodically unfavourable conditions; and (ii) facilitation of high-SLA, small-seeded and tall plants in persistently severe environments. We suggest that facilitation related to herbivory will be idiosyncratic with respect to these functional traits.
4. Competition for limiting resources is predicted to reinforce trait-based responses to facilitation in periodically severe environments, particularly under light competition, but to offset facilitative effects to some degree in persistently severe environments. Thus, biotic interactions may have stronger consequences for shifts in trait distributions in environments typified by disturbance, pulsed soil moisture and short growing seasons limited by low temperatures.
5. Facilitative effects, in addition to facilitative responses, may also be regulated by functional traits, but there is much less empirical evidence for links between functional traits and ameliorative effects on the environment. However, we predict that leaf area index or other integrative traits related to canopy density are likely to be important effect traits for most facilitative mechanisms and should be integrated into more trait-screening programs.
6. Based on the exceptional contribution that trait-based approaches have made for understanding other interactions, we suggest that taking a functional comparative approach to facilitation is an opportunity to improve our ability to identify general patterns and consequences of positive interactions.

• Plant competition determines the diversity and species abundance of natural communities as well as potential yields in agricultural systems. Understanding the mechanisms of plant competition is instrumental to understanding plant performance in true vegetations.
• In this review, we will address various components of competition between plant individuals with a specific focus on molecular aspects. As plant–plant interactions during competition are multiple and complex, we will focus here on a restricted set of examples of plant traits that are thought to enhance their performance during competition.
• To respond to competition by neighbours, plants first need to detect these competitors in a reliable way. We discuss the various ways of molecular detection of competition through light-quality signals, nutrient levels, soluble root exudates and volatile organic compounds emitted by neighbouring plants. Once perceived, these signals are translated into responses such as shade avoidance, root foraging and allelopathy.
• We integrate the various molecular patterns of signal detection and subsequent plant responses, both above- and below-ground and including their interaction. We outline research strategies towards creating a general, mechanistic understanding of how plants increase their performance during competition.

1. The drivers behind plant competition and diversity have long been debated, and there is acceptance that soil micro-organisms may act as key drivers in plant interactions and community structure. The evidence for a microbial role in shaping plant interactions and communities will be considered here with emphasis on symbionts and pathogens.
2. Microbial populations are themselves strongly influenced by the plant community via the ‘rhizosphere’ effect. The rhizosphere community includes microbes both beneficial and detrimental to the plant. Both the ability of plants to cultivate different rhizosphere microbial populations and the resulting impact upon other plant species have largely been studied via ‘plant–soil’ feedback studies, a proxy necessitated by the fact the majority of soil micro-organisms are unculturable, but which nevertheless has rarely been used in conjunction with modern techniques to identify and quantify the micro-organisms involved.
3. Both microbial symbionts and pathogens can affect plant diversity and productivity, but the direct evidence for impacts on competitive interactions is surprisingly scarce. Evidence comes from biological invasions, the unintentional introduction of microbial pathogens to native plant communities and manipulative experiments under both field and controlled conditions. Pathogens generally have direct effects on plants, reducing their growth and so rendering them less competitive, whereas other symbionts may act by altering the availability of resources, with more subtle effects on competitive interactions.
4. Some of the best evidence for indirect effects comes from studies on arbuscular mycorrhizal (AM) fungi. New developments in our understanding of nutrient exchange in the arbuscular mycorrhizal symbiosis emphasize the need to view the fungal partners not as mere extensions of the plant. The suggestion that AM fungi may act to share resources among connected plants however remains to be proved.
5. Although plant competitive interactions can be driven by key microbial groups including symbionts and pathogens, knowledge gaps in the basic biology of these micro-organisms has hindered a full mechanistic understanding of these processes. If ecologists now embrace new technologies, significant advances in this area should be forthcoming.

1. Ocean acidification, caused by the uptake of atmospheric CO₂, is a threat to marine biodiversity, potentially rivalling the threat imposed by rising temperatures in some marine ecosystems. Although a growing body of literature documents negative effects of acidification on marine organisms, the majority of this work has focused on the effects of future conditions on modern populations, ignoring the potential effects of adaptation and physiological acclimatization.

2. We review current literature on the potential for adaptation to elevated pCO₂ in marine organisms. Although this body of work is currently quite small, we argue that data on the physiological effects of acidification, natural variation in pH and lessons learned from previous work on thermal adaptation can all inform predictions and priorities for future research.

3. Spatially varying selection is one of the most important forces maintaining intraspecific genetic variation. Unlike temperature, pH lacks a strong and persistent global gradient, and so selection may maintain less adaptive variation for pH than for temperature. On the other hand, we are only beginning to amass long-term data sets for pH variation in natural habitats, and thus, pH gradients may be more common than previously observed.

4. Two of the most important effects of elevated pCO₂ are reduced calcification and changes in metabolism. We discuss the ways that a detailed understanding of the physiological mechanisms underlying these effects is key to predicting the capacity for acclimatization and adaptation.

5. Important priorities for future research will be to assess local adaptation to pH conditions and to measure the capacity for adaptation to future acidified conditions in natural populations. Tools for this work include traditional quantitative genetics, transcriptomics and the adaptation of ion-sensitive field-effect transistor (ISFET) technology for use in continuous seawater pH monitoring in the field.

1. Rapid climate change both imposes strong selective pressures on natural populations – potentially reducing their growth rate and causing genetic evolution – and affects the physiology and development of individual organisms. Understanding and predicting the fates of populations under global change, including extinctions and geographical range shifts, requires analysing the interplay of these processes, which has long been a grey area in evolutionary biology.
2. We review recent theory on the interaction of phenotypic plasticity, genetic evolution and demography in environments that change in time or space. We then discuss the main limitations of the models and the difficulties in testing theoretical predictions in the wild, notably regarding changes in phenotypic selection, the evolution of (co)variances of reaction norm parameters, and transient dynamics.
3. We use two landmark examples of physiological responses to climate change –trees facing drier climate and extreme temperatures, and marine phytoplankton under rising CO₂ – to highlight relatively neglected questions and indicate the theoretical and empirical challenges that they raise. These examples illustrate notably that age-specific patterns of plasticity and selection on the one hand, and changes in community interactions and functioning on the other hand, need to be further investigated theoretically and empirically for a better understanding of evolutionary demographic responses to climate change in the wild.

1. Physical laws influence the ability of plants to exchange energy and mass with their external environments, which is influenced by the size and spatiotemporal display of surface area. In turn, energy–mass exchange rates affect plant growth and thus the consumption of resources and plant competitiveness.
2. Representative physical laws and processes are reviewed, and empirical data and computer models are used to elaborate on how energy–mass exchange rates, growth and competitiveness are interconnected.
3. Our review shows that biophysical constraints on energy–mass exchange rates significantly influence plant growth and plant–plant competition. We also show that biophysical constraints also provide opportunities for adaptation and species coexistence.

1. Terrestrial ectotherms are likely to face increased periods of heat stress as mean temperatures and temperature variability increase over the next few decades. Here, we consider the extent to which changes in upper thermal limits, through plasticity or evolution, might be constrained, and we survey insect and reptile data to identify groups likely to be particularly susceptible to thermal stress.

2. Plastic changes increase thermal limits in many terrestrial ectotherms, but tend to have less effect on upper limits than lower limits.

3. Although comparisons across insect species have normally not taken into account the potential for plastic responses, mid-latitude species seem most prone to experience heat stress now and into the future, consistent with data from lizards and other groups.

4. Evolutionary adaptive potential has only been measured for some species; there is likely to be genetic variation for heat responses in populations, but selection and heritability experiments suggest that upper thermal limits may not increase much.

5. Although related species can differ by several degrees in their upper thermal limits, there is strong phylogenetic signal for upper limits. If these reflect evolutionary constraints, substantial molecular changes may be required to increase upper thermal limits.

6. Findings point to many terrestrial ectotherms having a limited potential to change their thermal limits particularly within the context of an average predicted temperature increase of 2–4 °C for mid-latitude populations over the next few decades.

1. Plants have a complex immune system that defends them against attackers (e.g. herbivores and microbial pathogens) but that also regulates the interactions with mutualistic organisms (e.g. mycorrhizal fungi and plant growth-promoting rhizobacteria). Plants have to respond to multiple environmental challenges, so they need to integrate both signals associated with biotic and abiotic stresses in the most appropriate response to survive.
2. Beneficial microbes such as rhizobacteria and mycorrhizal fungi can help plants to ‘deal’ with pathogens and herbivorous insects as well as to tolerate abiotic stress. Therefore, beneficial microbes may play an important role in a changing environment, where abiotic and biotic stresses on plants are expected to increase. The effects of beneficial microbes on herbivores are highly context-dependent, but little is known on what is driving such dependency. Recent evidence shows that abiotic stresses such as changes in soil nutrients, drought and salt stress, as well as ozone can modify the outcome of plant–microbe–insect interactions.
3. Here, we review how abiotic stress can affect plant–microbe, plant–insect and plant–microbe–insect interactions, and the role of the network of plant signal-transduction pathways in regulating such interactions.
4. Most of the studies on the effects of abiotic stress on plant–microbe–insect interactions show that the effects of microbes on herbivores (positive or negative) are strengthened under stressful conditions. We propose that, at least in part, this is due to the crosstalk of the different plant signalling pathways triggered by each stress individually. By understanding the cross-regulation mechanisms we may be able to predict the possible outcomes of plant-microbe–insect interactions under particular abiotic stress conditions. We also propose that microbes can help plants to deal with insects mainly under conditions that compromise efficient activation of plant defences.
5. In the context of global change, it is crucial to understand how abiotic stresses will affect species interactions, especially those interactions that are beneficial for plants. The final aim of this review is to stimulate studies unravelling when these ‘beneficial’ microbes really benefit a plant.

1. In their natural environment, plants are faced with a multitude of attackers, of which insect herbivores and plant pathogens are an important component. In response to these attacks, plants release volatile organic compounds (VOCs), which play an important role in the communication between plants and the associated community members, such as other herbivores, phytopathogens and the natural enemies of herbivores.
2. While numerous studies have focused on either plant–pathogen or plant–insect interactions, less is known when these two sets of interactions co-occur. Depending on the mode of attack of the pathogen (necrotroph vs. biotroph) or herbivore (chewing vs. piercing-sucking) they will activate different defence pathways in the plant in which the phytohormones salicylic acid (SA), jasmonic acid (JA) and ethylene (ET) play key roles. As these pathways can crosstalk, a pathogen infection can interfere in a plant's defence response to herbivory, and vice versa.
3. Infestation of a plant with organisms inducing SA signalling prior to – or simultaneously with – attack by organisms that induce the JA pathway often suppresses JA signalling. However, the impact of this signalling pathway crosstalk on VOC induction is not clear cut, as there is high variability in the effects on volatile emissions, ranging from suppression to enhanced emission. The effects of the modified volatile blends on the foraging success of carnivorous natural enemies of herbivorous insects have started to be investigated. Foraging success of natural enemies generally withstands this modification of the host-induced VOC blend, but the presence or absence of key compounds is an important determinant of the response of certain carnivores.
4. Further studies incorporating plant–insect and plant–pathogen interactions at different levels of biological integration will provide valuable insight in how plants integrate signals from different suites of attacking organisms into an adaptive defence response.

1. Plant hormones play important roles in regulating plant growth and defence by mediating developmental processes and signalling networks involved in plant responses to a wide range of parasitic and mutualistic biotic interactions.
2. Plants are known to rapidly respond to pathogen and herbivore attack by reconfiguring their metabolism to reduce pathogen/herbivore food acquisition. This involves the production of defensive plant secondary compounds, but also an alteration of the plant primary metabolism to fuel the energetic requirements of the direct defence.
3. Cytokinins are plant hormones that play a key role in plant morphology, plant defence, leaf senescence and source–sink relationships. They are involved in numerous plant–biotic interactions.
4. These phytohormones may have been the target of arthropods and pathogens over the course of the evolutionary arms race between plants and their biotic partners to hijack the plant metabolism, control its physiology and/or morphology and successfully invade the plant. In the case of arthropods, cytokinin-induced phenotypes can be mediated by their bacterial symbionts, giving rise to intricate plant–microbe–insect interactions.
5. Cytokinin-mediated effects strongly impact not only plant growth and defence but also the whole community of insect and pathogen species sharing the same plant by facilitating or preventing plant invasion. This suggests that cytokinins (CKs) are key regulators of the plant growth-defence trade-off and highlights the complexity of the finely balanced responses that plants use while facing both invaders and mutualists.

1. Transmission from host to host is a crucial step in the life cycle of pathogens, particularly of viruses, ensuring spread and maintenance in host populations. The immobile nature of plants and the strong pectin and cellulose barrier surrounding cells have constrained most plant virus species to use vectors (mainly insects) for exit, transfer and entry from one host to another.
2. A growing body of evidence is showing that plant viruses can influence vector physiology and behaviour to increase their chances of transmission, either directly or through modification of the host plant. In contrast, little is known on the possible reciprocal interaction, where the vector way of life would significantly impact on the viral behaviour and/or phenotype within the infected plants, on its population genetics and its evolution.
3. The complex possible reaches of these three-way interactions on the ecology of each partner have not been exhaustively explored.
4. After briefly summarizing the current knowledge on how viruses can induce changes in insect vector behaviour, physiology and population dynamics, this review focuses on presenting unforeseen aspects related to (i) the impacts that the feeding habits of different insect vectors can have on the evolution of plant viruses and (ii) the possibility that vector-related stresses induce major switches in the ‘behaviour’ of viruses in planta, affecting primarily the efficiency of transmission by insect vectors.

1. Many plants are simultaneously attacked by arthropod herbivores and phytopathogens. These may affect each other directly and indirectly, enhancing or reducing the amount of plant resources they each consume. Ultimately, this may reduce or enhance plant performance relative to what should be expected from the added impacts of herbivore and pathogen when they attack alone.
2. Previous studies have suggested synergistic and antagonistic impacts on plant performance from certain combinations of arthropods and pathogens, for example, synergistic impacts from necrotrophic pathogens together with wounding arthropods because of facilitated infection and antagonistic impacts from induction of pathogen resistance by sucking herbivores.
3. We compiled published studies on the impact of plant–herbivore–pathogen interactions on plant performance and used meta-analysis to search for consistent patterns of impacts among plant, herbivore and pathogen characteristics and experimental conditions, and to test the suggested hypotheses on synergistic or antagonistic impacts.
4. None of the hypotheses based on proximate interactions between arthropods and pathogens were supported by our analysis; in contrast, the patterns we found were related to plant traits and experimental conditions.
5. Our results suggest that immediate loss of resources from interactions between arthropod herbivores and pathogens is generally moderated by compensation to an extent where there are no interactive effects on plant performance. However, as interactive impacts also differed among environments and parasite manipulation methods, this suggests that the ability of plants to compensate such losses may depend on environmental conditions and probably also overall infection load.

1. Plant pathogens and herbivores frequently co-occur on the same host plants. Despite this, little is known about the impact of their interactions on the structure of plant-based ecological communities.
2. Here, we synthesize evidence that indicates that plant pathogens may profoundly impact arthropod performance, preference, population dynamics and community structure across multiple spatial and temporal scales.
3. Intriguingly, the effects of plant–pathogen–herbivore interactions frequently cascade up and down multiple trophic levels and explain variation in the arthropod community at spatial scales ranging from patterns within single host plants to entire landscapes.
4. This review indicates that knowledge on pathogen–herbivore interactions may be crucial for understanding the dynamics of terrestrial communities.

1. Evolutionary adaptations in interactions between plants, microbes and arthropods are generally studied in interactions that involve only two of these groups, that is, plants and microbes, plants and arthropods or arthropods and microbes.
2. We review the accumulating evidence from a wide variety of systems, including plant- and arthropod-associated microbes, and symbionts as well as antagonists, that selection and adaptation in seemingly two-way interactions between plants and microbes, plants and arthropods and arthropods and microbes are often driven by the biotic context of a third partner.
3. We extend the concept of local adaptation from two-way interactions to scenarios for three-way interactions. We show that consumers can locally adapt to specific host phenotypes that are induced by a third species with which they do not directly interact. This emphasizes that indirect interactions have not only ecological but also important evolutionary consequences, and stresses the need to conduct studies of local adaptation in the proper ecological context of the species involved.
4. Overall, our review underlines the importance of three-way interactions in the evolution of plant–microbe, plant–arthropod and arthropod–microbe interactions, and we outline some promising directions for future research.

1. Invasive species are one of the great challenges facing the world leading to great economic losses. Increasing numbers of species introductions are also increasing the likelihood of new species interactions – particularly between plants, microbes and insects.
2. Frequently discovered interactions between plants, microbes and insects are giving rise to a new field: plant–microbe–insect (PMI) interactions. This paper focuses on novel PMI interactions created from the introduction of new plant, insect and microbe species. In particular, this paper asks: Do novel PMI interactions promote or inhibit invasive plants, microbes and insects? And can we predict whether novel PMI interactions are likely to become invasive?
3. While we might predict that novel PMI interactions are likely to be simple additive interactions due to their relatively short period of interaction, instead this review demonstrates that most novel PMI interactions are actually nonadditive. This manuscript shows that there are a great number of instances where invasive species are promoted by novel PMI interactions. By contrast, the studied cases where PMI interactions limit invasive species are predominantly biocontrol PMI interactions.
4. Future research on novel PMI interactions should focus on predicting future novel PMI interactions that promote invasive species. Given that many novel PMI interactions involve plant pathogens and their insect vectors, this novel PMI interaction deserves more focus. New research should also focus on non-novel PMI interactions that could be manipulated to hinder the spread of invasive plant, microbe and insect species.

1. The prevailing hypothesis states that treeline positions are defined by the direct effects of cold temperatures on cell division and tree growth. Meanwhile, photosynthesis is thought to be relatively unrestricted in treeline trees. Support for this hypothesis comes from the global correlation between temperature and treeline position, the observation that many treelines have advanced in response to recent warming and the frequent use of increment cores from treeline trees to reconstruct past climates. However, studies of the physiology of trees at the Arctic treeline are rare, and this hypothesis remains largely untested.
2. To improve our understanding of the relationships between temperature and performance of white spruce near the Arctic treeline, we made measurements of needle gas exchange, needle nutrition and soil nutrient availability over 2 years in three contrasting habitats: riverside terrace, hillslope forest and treeline. The sites had similar above-ground microclimates, but very different soil conditions. Soils were warm and dry on the terrace, cool and moist in the forest and cold and seasonally wet the treeline.
3. Photosynthesis, needle nitrogen (N) concentration and soil N availability declined from the terrace to the forest to the treeline. Low N availability at the treeline was likely a consequence of limited microbial activity in the cold and seasonally wet soils. Soils at the treeline were colder than the terrace during the growing season and colder than the forest in winter, when the treeline maintains a shallow snowpack.
4. Our results highlight the potential for an indirect effect of temperature on the growth of trees at the Arctic treeline and suggest that treeline responses to changes in climate may be more complex than previously thought.

1. Wood density (WD) affects plant biomechanics, drought and decay resistance. As a consequence, WD is an important functional trait related to plant demography and ecosystem processes, which is also used to estimate tree biomass. Radial variation in WD (changes from the centre of the stem to the cambium) affects the strength of the entire stem, but also reflects any changes in wood functional properties that might occur during a tree's lifetime.
2. To understand how WD and radial WD gradients, which were defined as the slope of the relationship between WD and distance to the centre, are related to demographic traits of species, we investigated WD in 335 tree species from a Panamanian moist forest and 501 species from an Ecuadorian rain forest and radial density gradients in 118 and 186 species, respectively, and compared WD with tree growth, mortality and size.
3. WD was negatively related to tree growth and mortality. WD tended to increase towards the outside in trees with low initial density and to decrease towards the outside in trees with high initial density. Radial WD gradients were largely unrelated to tree size and demographic traits, but some families had higher or lower WD gradients at a given inner WD.
4. Inner WD was by far the best predictor of radial WD gradients (r² = 0·39 for Panama and 0·45 for Ecuador) and this relationship was indistinguishable between the two rain forests. This suggests a broadly uniform function of WD variation, likely responding to mechanical requirements during ontogeny. We discuss the factors potentially driving radial increases or decreases in WD and suggest ways to elucidate the relative importance of tree mechanics, hydraulic safety or decay resistance.
5. We also discuss that not accounting for radial WD gradients may result in substantial errors in WD of the whole stem and consequently biomass estimates, and recommend sampling density gradients when obtaining density data from tree cores.

1. Reproductive success of parental care-providing species is contingent upon the level of parental investment into a brood. When the expected fitness contribution of a brood is outweighed by the costs of parental care (e.g. decreasing parent somatic condition), an individual may reduce its level of care, or may altogether abandon a brood in trade-off for potential future reproductive success. Leading parental care hypotheses have established parental stress, oxidative stress, nutrition and androgen condition, as well as reproductive value and the threat of brood depredation, as drivers of investment into parental care.
2. The concomitant effects of parent physiological condition and the threat of brood depredation have yet to be considered in their direct effect on the reproductive success of a parental care-providing individual. Using largemouth bass (Micropterus salmoides) as a model parental care-providing species, we investigated the relative influence of these factors, together, on a direct fitness measure: the decision by a parent to abandon its brood.
3. By employing a novel combination of multivariate and information-theoretic modelling, our findings indicate that reproductive success of parental largemouth bass is contingent primarily on the threat of depredation to a brood (i.e. the density of brood predators adjacent to nest locations), past investment into a brood and reproductive value of the brood.
4. Parent physiological condition had limited influence on the decision by largemouth bass to abandon parental care. Modelling indicated that parental circulating androgen concentration and antioxidant capacity may play a minimal role in driving brood abandonment; nutrition and stress condition of the parent did not differ between reproductive outcomes.
5. Findings here suggest that a holistic approach should be implemented when studying parental care and that a definite experimental endpoint, e.g., brood abandonment or reproductive success, be utilized as a direct metric of the cost to fitness of parental care decisions.

1. Ecological trapping implies a preference for low-quality habitats over higher-quality options. Although such a maladaptive decision-making has been shown in a range of organisms, the mechanisms that underlie this habitat selection pattern often remain unidentified. We tested in a human-modified environment whether food availability and food use of a migratory species operate as functional drivers of an ecological trap.
2. The Red-backed shrike (Lanius collurio) is a migratory bird that was shown to breed preferentially in forest plantation clearcuts where reproductive performance is however markedly lower than in the traditional farmland habitat. We examined whether differences in food availability between forest and farmland habitats resulted in contrasting food provisioning to the offspring with, in turn, significant impact on the quality of the offspring.
3. Invertebrate prey items for shrikes were 41% more abundant in farmland, and prey size was 6% larger in forest habitat. Opposite to the pattern of prey size availability, larger prey items were delivered to the offspring in farmland than in forest habitat. Feeding visits by the parents were 22% more frequent in farmland, and evidence of strong among-nestling competition for food was found in forest only.
4. This study demonstrates the existence of food limitation for an organism in a habitat type associated with high preference but low reproductive performance. This result offers a functional explanation for the mismatch between habitat preference and quality, and hence, for an ecological trap in the wild.
5. Beyond the case of migratory birds, this study draws attention to the point that human-modified environments may lead to a biased perception of habitat quality relative to food availability and may induce an ecological trap for organisms that allocate only a limited time budget to habitat selection decision-making.

1. To gain insight into the foraging behaviour of deep diving seals, we developed a long-term jaw-motion recorder, which successfully measured the feeding attempts of four post-breeding female northern elephant seals for 55–68 days during migration in the north-east Pacific Ocean.

2. Using the jaw-motion recorders in conjunction with satellite tracking data, we first reveal the three-dimensional fine-scale distribution of deep foraging activity in the north-east Pacific Ocean.

3. A large number of jaw-motion events (23 817–58 766 during 2925–4178 dives, per seal) were observed with diel patterns suggesting their dependency on small mesopelagic prey. Calculations using at-sea field metabolic-rate and the photographs concurrently obtained by the head-mounted camera indicated feeding on small mesopelagic prey (10–20 g) including lantern fish (F. Myctophidae).

4. The foraging behaviour of the northern elephant seal contrasts with echolocating toothed whales, which make fewer feeding attempts, suggesting the whales forage more selectively. We hypothesize that the continuous diving mode exhibited by this seal could be attributed to their reliance on small prey and their less efficient ‘passive sensors’ for prey search, that is, their vision or whiskers to detect prey.

1. The overwhelming focus of studies on communication has been on interactions among conspecifics. However, communication is often selected by a complex network of disparate intended perceivers and eavesdroppers belonging to multiple species. Shifting towards a multiple-perceiver paradigm requires a framework to compare the perception of signals across the different community members. Here, we present the stimulation landscape, a generalist model that achieves this goal.
2. A stimulation landscape consists of a multidimensional space describing every possible stimulus for a given signalling system, to which is added one dimension indicating for each stimulus its conspicuousness for a given perceiver. Random sampling of stimuli in the landscape then allows computing a reference distribution of conspicuousness, which is used to standardize the observed conspicuousness.
3. The stimulation landscapes corresponding to the different perceivers participating in a communication system all have the same dimensionality and scaling. They can thus be combined to describe the amalgamation of the selective forces exerted on a signal by the distinct sensory systems of multiple perceivers.
4. We detail the model in the context of colour signalling and apply it to the case of sexual communication in songbirds. Songbirds have a different visual system than their main predators, the birds of prey. We therefore asked whether songbirds evolved colour signals that can mediate the trade-off between sexual selection exerted by conspecifics and natural selection exerted by birds of prey. We show that yellow – not ultraviolet colours as previously thought – maximize the difference of conspicuousness to songbirds and to birds of prey, but that the perceptual similarities between these two groups generally hamper the evolution of private visual communication in songbirds.
5. The stimulation landscape is a valuable tool to investigate the role of communication in structuring the large networks of interactions between species. We further show that the stimulation landscape is related to the evolutionary model of adaptive landscape. By explicitly addressing communication in a community context, the stimulation landscape contributes to bridge the current gap between evolution and ecology.

1. Subordinates in cooperative breeding systems may provide help to dominant pairs, who can benefit by either an increased total investment in their current brood or a reduced personal contribution to this investment. In the social cichlid Julidochromis ornatus, one large male subordinate generally spends 90% of his time in close proximity to the breeding shelter, whereas the dominants only spend 50% of their time close to the shelter.
2. We experimentally removed the large subordinate for 30 days (approximating one breeding cycle) to study the investment strategies of dominants and the effects on offspring survival, while accounting for subordinate immigration. Experimental groups were compared with control groups, from which subordinates were also caught but not removed. On day one following removal, we tested whether dominants overcompensated, fully compensated or undercompensated for absence of the subordinate on several parental behaviours. Moreover, we tested whether the pairs' potential compensatory behaviour remained high seven days following large subordinate removal.
3. One day following removal, dominants increased their time spent in the territory and their frequency of breeding shelter visits and defence, compared with the pre-removal phase and control groups. The dominant pair overcompensated for the loss of subordinate help in their breeding shelter visits, fully compensated in defence and undercompensated their time spent in the territory. Seven days after large subordinate removal, behavioural differences between treatments had disappeared. However, when distinguishing between groups with or without a new immigrant subordinate, dominant pairs only diminished investment in the presence of an immigrant, suggesting a compensatory role of the large subordinate. Finally, survival of juvenile group members was not affected by the treatment.
4. Our experiments indicate that the presence of a large subordinate does not increase the dominant pairs' current reproductive success, but instead allows them to reduce their personal contribution to investment in the current brood. In addition, we illustrate that dominants may show strikingly different compensatory responses depending on the type of behaviour and emphasize the importance of immigrant subordinates to relieve dominants from costly compensatory responses in cooperative breeding systems.

1. The terminal investment hypothesis has two predictions: in the face of an infection (i) mature males will increase investment to traits that increase mating success, while such investments will occur to a less extent in young males; and (ii) physiological costs of resource reallocation will be more severe for infected mature males than for infected young males.
2. Although these predictions have been tested in long-lived vertebrates, prior studies have not examined actual resource allocation conflicts. Here, we have tested the above predictions and have investigated the energetic costs of increased mating by old males, using a short-lived invertebrate, the damselfly Hetaerina americana. Males of this species defend territories as the main way to obtain access to females.
3. Using groups of infected vs. noninfected males of two different ages, we found that compared to young infected males, mature infected males defended territories for longer, had higher mating success and directed agonistic behaviour to conspecific males more frequently. Despite similar immune responses by mature and young males, infected mature males ended up with less fat reserves compared to infected young males. This suggests that resource allocation conflicts are more severe for mature than for young males.
4. In general, these results suggest that the terminal investment hypothesis applies in males of short-lived invertebrates and that a cause of increased mating success for males of advanced ages is reduced energetic stores.

1. Some animals migrate huge distances in search of resources with locomotory mode (flying/swimming/walking) thought to drive the upper ceilings on migration distance. Yet in cross-taxa comparisons, upper ceilings on migration distance have been ignored for one important group, sea turtles.
2. Using migration distances recorded for 407 adult and 4715 juvenile sea turtles across five species, we show that for adult cheloniid turtles, the upper ceiling on species migration distances between breeding and foraging habitats (1050–2850 km across species) is similar to that predicted for equivalent-sized marine mammals and fish.
3. In contrast, by feeding in the open ocean, adult leatherback turtles (Dermochelys coriacea) and juveniles of all turtle species can travel around 12 000 km from their natal regions, travelling across the widest ocean basins. For juvenile turtles, this puts their maximum migration distances well beyond those expected for equivalent-sized marine mammals and fish, but not those found in some similar sized birds.
4. Post-hatchling turtles perform these long-distance migrations to juvenile foraging sites only once in their lifetime, while adult turtles return to their breeding sites every few (generally ≥2) years. Our results highlight the important roles migration periodicity and foraging mode can play in driving the longest migrations, and the implications for Marine Protected Area planning are considered in terms of sea turtle conservation.

1. Much of the theory on offspring size focuses on the effects of habitat quality on the relationship between offspring size and fitness. Habitat spacing may be another important factor that affects selection on offspring size when offspring disperse prior to colonization and accrue deferred costs that are mediated by offspring size.

2. We developed a theoretical model, based on a well-known optimality model, of how selection on offspring size changes with dispersal distance. The model assumes that offspring fitness depends on both offspring size and dispersal duration and that dispersal time and distance are positively related. Such assumptions are based on thousands of marine invertebrate species with non-feeding larvae, but our model also applies more generally to any organism where offspring size modifies the energetic costs of dispersal, and there is a positive relationship between dispersal duration and distance.

3. Our model predicts that, even when habitat quality does not vary, more isolated habitats may favour the production of fewer, larger offspring if smaller offspring incur greater deferred costs of dispersal. We then empirically demonstrate that offspring size and dispersal duration have interactive effects on post-settlement survival in a marine invertebrate (Bugula neritina), and such size-dependent deferred costs of dispersal are of a magnitude sufficient enough to potentially favour larger offspring in isolated habitats.

4. Together, our results indicate that the spatial pattern of suitable habitat could impose very different selective regimes on offspring size compared with the effects of habitat quality. Furthermore, our predictions contrast to those predicted for seed size and dispersal in plants, where the production of smaller, more numerous seeds is often a more efficient way for mothers to access distant, suitable habitat.

1. Nest-site location is a critical component of habitat preference in birds, reflecting a balance between minimizing the likelihood of nest predation while maximizing access to nutritional resources. While many studies have demonstrated the influence of predators in nest-site selection, few studies have explicitly quantified nutritional resources or considered the interacting effects of predation and food availability in determining nest survival.
2. The painted honeyeater Grantiella picta is a mistletoe-specialist frugivore, with fruit from grey mistletoe Amyema quandang representing the main food source for breeding adults and nestlings. Previous work demonstrated that painted honeyeaters prefer to place their nests within mistletoe substrates. Here, we measured the outcome of 63 nests over two years, relating survival to various structural and resource-based variables to discern whether nests placed in mistletoes were more likely to succeed.
3. Twenty-one nests survived the 33 day nest period, with 35 of the 42 failed nests predated. While few significant differences were discerned between successful and unsuccessful nests in terms of nest tree or surrounding habitat, nest substrate emerged as the most important predictor of nest fate. Survival of nests in mistletoe was 16·6% across a 33 day active nest period compared with a mean of 43·1% for nests in other substrates, a difference consistent across both years.
4. Rather than having a positive effect on nest outcome (via access to nutritional resources), proximity to mistletoe had a marked negative effect, with nests in mistletoe suffering a predation rate 2·6 times higher than nests elsewhere. Rather than predators targeting mistletoe clumps, we suggest that this pattern arises from other species visiting fruiting mistletoe clumps, opportunistically predating the nest contents and disturbing attending parents. We interpret this finding as evidence that the painted honeyeater may be caught in an ecological trap; the cues used to select nesting locations are a poor predictor of success.

1. Rodents frequently forage in a density-dependent manner, increasing harvesting in patches with greater seed densities. Although seldom considered, seed harvesting may also depend on the species identities of other individuals in the seed neighbourhood. When the seed harvest of a focal species increases in association with another seed species, the focal species suffers from Associational Susceptibility. In contrast, if seeds of the focal species are harvested less when in association with a second species, the focal species benefits from Associational Resistance.
2. To evaluate density dependence and associational effects among seeds in mixtures, we conducted seed removal experiments using a completely additive design patterned after a two-species competition experiment using seeds of either Achnatherum hymenoides (Indian ricegrass), Leymus cinereus (basin wildrye) or Pseudoroegneria spicata (bluebunch wheatgrass), all native perennial grasses, combined with seeds of Bromus tectorum (cheatgrass), a non-native annual grass. The experiment involved placing five fixed quantities of the native seeds mixed with five fixed quantities of B. tectorum seeds in a factorial design, resulting in 35 seed mixture combinations. The seed-eating rodent community at our study sites, in order of abundance, is composed of Peromyscus maniculatus (North American deer mouse), Dipodomys ordii (Ord's kangaroo rat) and Perognathus parvus (Great Basin pocket mouse).
3. Native seed harvesting was density dependent, with a greater proportion of seeds being harvested as density increased. In the mixed density model, the presence of B. tectorum did not affect harvest of any of the native species' seeds when analysed individually. However, when all three native species were analysed together, increasing quantities of B. tectorum resulted in reduced harvest of native seeds, demonstrating weak but significant Associational Resistance. In contrast, harvest of B. tectorum seeds increased when in combination with any of the native seed species individually, indicating relatively strong Associational Susceptibility.
4. These results demonstrate that seed harvest is determined not just by seed density, but also by the local seed neighbourhood and suggest that associational effects between native seeds and B. tectorum can occur in field conditions. The ecological implications of seed selection and associational effects on plant populations in natural and managed systems are also discussed.

1. Animal ecology could benefit from a well-defined trait-based framework, mostly applied in plant ecology, to further develop predictions of animal communities under various environmental conditions. We extended the functional approach to a multitrophic system by combining plant and ant traits in relation to environmental conditions to study the relationships between these three components.
2. We sampled plant and ant abundances along an aridity gradient in grazed and ungrazed conditions in the arid steppes of eastern Morocco. We measured five plant functional traits related to water stress and grazing resistance and six ant functional traits related to body size, dispersal and behaviour. We related each component (environment, vegetation and ants) using Mantel partial correlations to uncover the causal structure between components and using a fourth-corner analysis to describe the effects of the environment and vegetation on ant communities.
3. Results indicated that vegetation had a direct effect on ant community composition while the environment only had an indirect effect on ant community composition through vegetation structure. This result was consistent when looking at both the taxonomic and functional composition of communities, but correlations were stronger when based on taxonomic composition. Aridity was the variable most significantly linked with ant functional traits
4. Synthesis. The use of functional traits in animal ecology is relatively new, and an increase in trait-based community ecology studies that include more than one trophic level would be beneficial in identifying trait-based patterns in multitrophic communities. This new approach could become very useful in identifying mechanistic explanations of multitrophic community assembly and making predictions about their evolution under changing environmental conditions. It could also be of practical use in conservation biology in assessing habitat quality.

1. Phenotypic flexibility is a major mechanism in compensating climate-driven changes in resource availability. Heterotherms can use daily torpor to overcome resource shortages and adverse environmental conditions. The expression of this adaptive energy-saving strategy varies among individuals, but the factors constraining individual flexibility remain largely unknown.
2. As energy availability depends on individual stores and/or on the ability to acquire food, the propensity and flexibility in torpor use are expected to be constrained by body condition and/or size, respectively. The aim of this study was to test whether the dependency of torpor depth on air temperature was constrained by body condition and/or body size in a small heterothermic primate, the grey mouse lemur (Microcebus murinus). During the onset of the dry season, we monitored air temperature as well as skin temperatures of 14 free-ranging individuals (12 females, two males) of known body mass and size.
3. Unexpectedly, torpor depth depended as much on air temperature as on body condition and size. Fatter, or larger, mouse lemurs underwent deeper torpor than smaller, or leaner, ones. Individual reaction norms of torpor depth to air temperature also revealed that the propensity to undergo deep torpor and the flexibility in torpor depth were enhanced by large body size and high body condition, whereas small, lean individuals remained normothermic.
4. Our study illustrates that alternative physiological strategies to overcome temperature constraints co-occur in a population, with body size and condition being key determinants of the energy conservation strategy that an individual can launch.

1. Reproduction and immune function are critical processes, but organisms can rarely optimize both traits. Resultant reproduction–immunity trade-offs may be ‘facultative’, occurring only when resources are scarce, or they may be ‘obligate’, occurring regardless of resource availability.
2. Previous research has tested for the ‘facultative’ or ‘obligate’ nature of reproduction–immunity trade-offs by measuring resource allocation (e.g. follicle size). However, measuring resource allocation alone may be insufficient when gauging the fitness consequences of reproduction–immunity trade-offs because the number and quality of eggs or offspring trade off with one another.
3. We used the Texas field cricket (Gryllus texensis) to provide the most direct test to date of whether a fitness trade-off between these two traits is ‘facultative’ or ‘obligate’. We used a factorial design to manipulate food availability and immune status throughout adulthood. We then estimated lifetime fecundity, hatching success and their product (reproductive success), and we also measured several aspects of offspring quality (e.g. egg size and protein content, and hatchling size and energy stores).
4. A reproduction–immunity trade-off was ‘obligate’ in this species because immune challenge reduced reproductive success estimates regardless of food availability. Females with unlimited food were more fecund and produced more and larger hatchlings, but neither food availability nor immune status affected egg size, egg phenoloxidase activity, incubation duration, hatching success or hatchling energy stores. We observed a trade-off between offspring size and number – females favouring offspring size over fecundity produced fewer hatchlings, but their hatchlings were of higher quality (larger and more robust).
5. By demonstrating that not all eggs are created equal, we provide key insight into the role of reproductive allocation in the fitness trade-off between reproduction and immunity.

1. Ecological stoichiometry, that is, the study of mass balance of multiple key chemical elements during ecological interactions, has recently been generalized to most ecosystems. Yet, effects of stoichiometric constraints on the life-history traits of detritivores, one of the most important trophic level through its importance in nutrient cycling, are still poorly documented.
2. Forested headwater streams constitute representative detritus-based ecosystems, relying on leaf litter inputs as the main energy and nutrient source for their functioning. Leaf litter is quickly colonized by aquatic hyphomycetes, which are known to improve the quality of detritus, enabling nutrient and energy transfer to higher trophic levels.
3. In this study, we manipulated leaf litter nutrient content of two common riparian tree species, differing in their initial biochemical composition, by short-term phosphorus addition to leaf litter precolonized by aquatic hyphomycetes. Then, we tested the impact of leaf litter phosphorus content on some key life-history traits, homeostasis and growth, of a common detritivorous invertebrate, Gammarus fossarum (Crustacea Amphipoda).
4. G. fossarum fed individually for 5 weeks with P-enriched leaf litter showed higher survival and growth rates than organisms fed with leaf litter colonized by fungi without P addition. Phosphorus content of resources did not alter G. fossarum elemental composition, suggesting that these detritivores are able to maintain their elemental homeostasis.
5. This study sheds new light on the importance of phosphorus content of detritus for detritivores and paves the way for further studies aimed at transferring ecological stoichiometry concepts to detritus-based ecosystems.

1. Many prey species are chemically defended and have conspicuous appearance to deter predators (i.e. aposematism). Such warning signals work because predators pay attention to the colour and size of signals, which they associate with unprofitability.
2. Paradoxically, in early life stages, aposematic species are often warningly coloured, but their chemical defences are lacking because they have yet to be acquired through the diet or synthesized endogenously. This state of being conspicuous yet poorly defended must place individuals at increased risk of predation, but how they minimize this risk during development is unclear.
3. We reared larval green and black poison frogs (Dendrobates auratus) on a relatively low or a higher food supply and tested the hypothesis that individuals with more resources should grow larger while reducing their investment in warning signals at metamorphic completion. We also assayed markers of oxidative balance (malondialdehyde, superoxide dismutase and total antioxidant capacity) to ascertain whether there were resource-allocation trade-offs that differed with diet treatments.
4. Low-food froglets were relatively small, and their body size and signal luminance (perceived brightness) were positively correlated. In contrast, in high-food froglets body size and warning signal luminance were negatively correlated, suggesting either a resource-allocation trade-off or alternatively a facultative reduction in luminance exhibited by larger froglets.
5. The reduction in luminance in relatively large, high-food froglets did not appear to arise because of oxidative stress: signal luminance and markers of oxidative stress were positively correlated in high-food froglets, but were negatively correlated in low-food froglets suggesting a trade-off.
6. Our results highlight developmental plasticity in body size and coloration as affected by resource (i.e. food) supply. Such plasticity seems likely to minimize predation risk during the vulnerable period early in life when individuals are warningly coloured and must make the transition from an undefended phenotype to a mature aposematic state.