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- Materials and Methods
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The field of macroecology relies heavily on the concept of range size, which measures how widely distributed a taxon or lineage is (Gaston & Blackburn, 2000). The efforts of ecologists focus largely on narrowly distributed taxa, that is, on only one end of the range-size spectrum (Gaston, 1994). While this focus is very much justified from a conservation perspective, it is less easy to justify the lack of a substantial contemporary body of literature pertaining to the opposite end, namely naturally very widespread taxa or lineages. Indeed, although these taxa are typically not of conservation concern, an understanding of their success would be relevant to the growing field of invasion biology (Stohlgren et al., 2011), and furthermore of great interest in telling the story of life on Earth, in particular where range expansion meant colonizing the world's less hospitable environments and isolated landmasses.
The phrase ‘cosmopolitan taxa’ describes an old intuitive concept, referring to organisms spread globally, or nearly so. De Candolle (1855) was possibly the first to use the term cosmopolitan in a biogeographical sense. Only recently have there been attempts to define this phrase in an evolutionary perspective (for example Hoffmann, 1996, considers cosmopolitan cyanobacteria to include those groups in which dispersal happens more rapidly than evolution) or to model cosmopolitan distributions (Goldberg, 2007, looking at the age of endemic versus cosmopolitan lineages). Lists of cosmopolitan (or ‘widely distributed’) organisms usually refer to taxa such as species, genera or families (e.g. Darlington, 1957; Good, 1964; Fenchel & Finlay, 2004). However, in a broad evolutionary perspective, one should of course be looking at lineages. Every organism belongs in fact to a cosmopolitan lineage, the question being how inclusive that lineage needs to be to meet a given criterion for being classified as cosmopolitan. For example, the osprey (Pandion haliaetus) can be described as a cosmopolitan species; on the other hand, groups such as shrews (Soricidae) are also cosmopolitan, but it may take the entire family to give them this status, and the family includes hundreds of species, most of which have narrow geographical ranges. Accordingly, the tree of life can be subdivided into cosmopolitan groups (groups defined so as to be minimally inclusive while still meeting a given criterion for being called cosmopolitan) and grades of less widely distributed lineages leading up to these.
Recently, a number of case studies have investigated the historical biogeography of specific cosmopolitan lineages using molecular methods (Richardson et al., 2004; Funk et al., 2005; Bossuyt et al., 2006; Lovette & Rubenstein, 2007; Pramuk et al., 2008; Voelker et al., 2009). These studies often indicate the successive colonization of multiple regions, and in some cases remarkable long-distance dispersal events. This raises the following question. Are all or most cosmopolitan lineages the result of dispersal from a centre of origin, or can at least some of them be explained by vicariance, with lineages surviving in multiple landmasses following the break-up of Pangea?
If dispersal is the only (or main) explanation, then organisms with better dispersal abilities should be more likely to attain cosmopolitan status rapidly, and consequently these groups should require fewer species to make a lineage cosmopolitan. Furthermore, for lineages that are found in most parts of the world but not in the remaining few, these areas of absence could be relevant. Under the dispersal scenario, the proportion of lineages that are cosmopolitan in more isolated landmasses is likely to be different from that in well-connected ones. Absence from areas with limiting environmental factors (aridity, cold climates), on the other hand, would not differentiate between vicariance and dispersal scenarios.
Under the dispersal scenario, the centre of origin for each cosmopolitan lineage can be sought by examining the distribution of the lineage that is sister to the cosmopolitan one, and if many such sister lineages occur in the same restricted regions, this could be indicative of a repetitive process of global colonization starting from these regions. This pattern has often been implied in phrasings such as ‘out of Africa’, ‘out of Australia’ or ‘out of Asia’ (Waters & Roy, 2004; Braby & Pierce, 2007; Donoghue, 2008), although no cross-lineage tests for such hypotheses have focused specifically on cosmopolitan lineages.
In this study, we use geographical and phylogenetic mapping of cosmopolitan lineages in tetrapod vertebrates (chosen as a study group by virtue of the availability of good distributional data) to answer these questions. First, in a descriptive effort, we list all cosmopolitan terrestrial tetrapod minimum-spanning lineages. Second, we perform phylogenetic and geographical mapping exercises, testing the following predictions: (1) regions that were historically isolated for long periods of geological time, such as Australia and South America, have a low representation of cosmopolitan clades (and thus more ‘original’ vertebrate faunas); (2) regions with extreme environmental conditions (either low temperatures or low precipitation), as well as recent and isolated oceanic islands, contain a greater proportion of cosmopolitan lineages (less ‘original’ faunas); (3) cosmopolitan lineages originate more often in certain regions of the world, irrespective of their intrinsic characteristics (the ‘out of…’ hypothesis); and (4) the number of species in cosmopolitan lineages is influenced by average body size and the ability to fly. Third, we discuss these results in the light of the available lineage age data.
Materials and Methods
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- Materials and Methods
- Supporting Information
Three criteria based on two data sets were employed in deciding what lineages can be considered cosmopolitan. Initially, in an exploratory phase, relevant distributional data sources (Nowak & Paradiso, 1983; Halliday & Adler, 1986; Del Hoyo et al., 1992 onwards; Perrins, 2009; Roberson, 2009; AmphibiaWeb, 2010; Frost, 2010; Uetz & Hallermann, 2010) and phylogenetic references (see Appendix S1 in Supporting Information) were browsed, and the distribution of monophyletic lineages was mapped for equal-area cells (identical in coverage to those used in the worldmap software; Williams, 1999). After preliminary trials, mapping was restricted to those cells located between 60° N and 60° S that contain at least 10% land. This resulted in 281 cells (Appendix S2). In order to approximately match the occupancy levels used in previous, intuitive approaches, lineages were considered cosmopolitan if present in at least 215 of these 281 cells (76.5%) (criterion a). If a lineage fell short of meeting this criterion, further sister lineages were included, until either the criterion was met, or a node in the tree was reached where the sister lineage was already a cosmopolitan lineage. The lineages thus identified as cosmopolitan or nearly so were then mapped using the WildFinder data set (World Wide Fund for Nature, 2010), a comprehensive presence/absence data set for tetrapod vertebrate species in 821 terrestrial biogeographical subdivisons of the world, termed ‘ecoregions’, intuitively delimited by Olson et al. (2001). Based on the distributional information in this data set, lineages were considered cosmopolitan if present in at least 500 (60.9%, criterion b) or at least 600 (73.1%, criterion c) of the 821 ecoregions. While it can be argued that the geographical units in each of the two data sets are less than perfect (unequal dry land area in both cases, incomplete distributional data in mapping lineages in the former, and intuitive predefined boundaries for the latter), the use of both gave us some assurance that our results were not simply driven by drawbacks in the way the distributional data were assembled. The WildFinder data conveniently allowed us to calculate lineage distribution and diversity, and to map lineages in ArcGIS (ESRI, 2008) within a manageable number of units. Consequently, lineages meeting any of the three criteria are listed and used in the phylogenetic mapping, but only lineages identified using criteria (b) and (c) [thus using World Wild Fund for Nature's (WWF) WildFinder data] are used in the geographical mapping exercises.
To assess the representation of cosmopolitan lineages in the WWF ecoregions, we first visually inspected the distributional maps produced for individual lineages, looking for patterns indicative of historical and environmental limitations. We then calculated the number of lineages present in each ecoregion; next the numbers of species in all cosmopolitan lineages were added for each ecoregion; and finally this sum was divided by the total number of tetrapod species in that ecoregion to give a measure of proportional representation.
To assess the geographical origin of cosmopolitan lineages, we assumed that this would most often be the area where closely related but less widespread lineages occur (cf. for example Erwin, 1985). In order to identify this area, one should ideally consider the distribution of multiple lineages diverging from the cosmopolitan lineage as its occupancy increases. Owing to the lack of a fully resolved phylogenetic tree, here the sister lineage of each cosmopolitan lineage was identified and mapped. To identify world regions where multiple cosmopolitan lineages originated, we calculated (1) the total number of sister lineages, (2) the number of range-restricted lineages (sister lineages present in fewer than 120 ecoregions, this value being based on the most notable inflection point in a histogram of sister lineage range sizes; graph not presented here), and (3) the total number of species belonging to sister lineages present in each ecoregion.
The total number of sister lineages was calculated (i) unweighted, as well as weighted by range size, which was achieved by dividing each presence by the total number of ecoregions where that specific sister lineage was present; the number of ecoregions being (ii) untransformed, (iii) square-root-transformed, or (iv) log-transformed (see Williamson & Gaston, 1999). This weighting was aimed at giving greater value to those ecoregions in which multiple range-restricted sister lineages occur.
In assembling information on phylogenetic relationships, sister lineages were determined from the most detailed source in each case. Where two distinct phylogenetic studies were available, the more recent one was preferred, and where the studies were less than 3 years apart, we chose the tree with higher support values. Where more than two phylogenetic studies were available, we followed the one presenting results closest to a putative cross-study consensus tree. In the very few cases where no phylogeny was available, we used taxonomy as a surrogate (see Appendix S1 for reference details). We considered only those references published (at least online) by October 2011, when analyses and mapping were performed.
To assess the importance of body mass and flight in attaining cosmopolitan status, the numbers of species needed to make a lineage cosmopolitan (according to criterion b) were compared across the following categories: (1) flight versus no flight (all bird and bat lineages listed here are dominated by species that have the ability to fly), and (2) < 10 g; 10–100 g; 100 g–1 kg; > 1 kg, using spss 21.0 (IBM Corporation, 2012). Body mass for a lineage was recorded as the estimated cross-species average for adult body mass for all species in the lineage, derived from the same references as the geographical distribution [listed under criterion (a) above].
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Eighty-three lineages were identified that met at least one of the three criteria for being cosmopolitan. Of these, only 24 belonged to groups other than birds (Fig. 1, Table 1). Cosmopolitan lineages were particularly numerous in water birds (waders, herons) and raptors; in some of these cases, such lineages were represented by single species (e.g. great egret, osprey, peregrine). Of these 83 lineages, 77 were cosmopolitan according to criterion (b), occurring in at least 500 ecoregions. When increasing this number to 600 (criterion c), 17 lineages remained cosmopolitan in their original form, 28 had to be expanded by incorporating further sister lineages (in four cases, these included other cosmopolitan lineages), and the rest were disqualified (see Table 1 for cosmopolitan lineages; Appendix S1 for sister lineages).
Table 1. Listing of the cosmopolitan terrestrial tetrapod vertebrate lineages mapped on the phylogeny in Fig. 1, indicating whether they fulfil criteria (a), (b) and/or (c) for being considered cosmopolitan
|Lineage||Criterion (b)||Criterion (c)|
|Number||Name||Description||Number of ecoregions occupied||Number of species||Description||Number of ecoregions occupied||Number of species|
| 1||Common frog||Ranoidea||701||951||As for (b)||701||951|
| 2||Toad*||Core Bufonidae||561||201||Bufonidae, Dendrobatidae, Leptodactylidae, Centrolenidae, Allophrynidae||603||1478|
| 3||Shrew||Soricidae||562||312||Not cosmopolitan|| || |
| 4||Free-tailed bat****||Molossidae||548||98||Not cosmopolitan|| || |
| 5||Mouse-eared bat||Core Myotis||599||97||Myotinae, Kerivoulinae, Murininae||637||134|
| 6||Serotine bat||Nycticeiini||510||44||Nycticeiini, Pipistrellini||714||181|
| 7||Barbastelle*||Lasiurini, Plecotini||523||31||Not cosmopolitan|| || |
| 8||Hare||Core Leporidae||558||54||Not cosmopolitan|| || |
| 9||Mouse||Muridae, Cricetidae||715||1130||As for (b)||715||1130|
|10||Squirrel||Core Sciuridae||561||271||Sciuridae, Aplodontiidae, Myoxidae||601||303|
|11||Deer||Cervidae, Moschidae, Bovidae||639||187||As for (b)||639||187|
|12||Cat*||Core Felinae||523||16||Core Felidae||606||30|
|15||Otter||Lutrini||509||12||Included in above|| || |
|16||Gecko*||Geckonidae||516||695||Not cosmopolitan|| || |
|17||Skink||Scincidae||588||1224||Not cosmopolitan|| || |
|18||Common lizard||Laterata||501||962||Not cosmopolitan|| || |
|19||Chameleon|| Iguania ||555||1021||Not cosmopolitan|| || |
|20||Adder||Viperidae||512||237||Not cosmopolitan|| || |
|21||Cobra****||Elapidae, Lamprophiidae||549||844||Not cosmopolitan|| || |
|22||Grass snake****||Natricidae||521||516||Colubridae s. str., Natricidae||615||1188|
|23||Smooth snake||Core Colubridae s. str.||572||577||Included in above|| || |
|24||Turtle||Testudines||528||286||Not cosmopolitan|| || |
|25||Partridge*||Core Phasianidae||566||159||Not cosmopolitan|| || |
|26||Goose||Not cosmopolitan|| || ||Not cosmopolitan|| || |
|27||Shoveller||Anas clypeata group||608||9||As for (b)||608||9|
|28||Mallard***||Anas platyrrhynchos group||512||8||Core Anas||621||20|
|29||Dove||Columbinae||607||77||As for (b)||607||77|
|30||Dabchick*|| Tachybaptus, Podilymbus ||617||6||As for (b)||617||6|
|32||Nightjar*||Chordeiles, Caprimulgus and related genera||622||41||As for (b)||622||41|
|33||Cuckoo||Cuculiformes||701||141||As for (b)||701||141|
|34||Crake*||Core Porzana, Crex||500||10||Not cosmopolitan|| || |
|35||Coot||Not cosmopolitan|| || ||Core Gallinula, Fulica||639||17|
|36||Moorhen||Core Gallinula||525||4||Included in above|| || |
|37||Cormorant**||Phalacrocoracidae, Anhingidae, Sulidae||518||44||Not cosmopolitan|| || |
|38||Ibis||Not cosmopolitan|| || ||Not cosmopolitan|| || |
|39||Night heron****|| Nycticorax nycticorax ||503||1||Not cosmopolitan|| || |
|40||Bittern*||Core Ixobrychus||526||7||Core Botaurinae||642||12|
|41||Little egret****||Core Egretta||549||3|| Egretta, Ardeola ||609||17|
|42||Great egret|| Chasmerodius ||563||1||Not cosmopolitan|| || |
|43||Grey heron||Ardea cinerea group||613||4||As for (b)||613||4|
|44||Stilt****||Recurvirostridae||538||7||Recurvirostridae, Ibidorrhynchidae, Haematopodidae||601||21|
|45||Ringed plover||Charadrius hiaticula group s. str.||526||5||Charadrius hiaticula group s. lat.||667||9|
|46||Lapwing||Not cosmopolitan|| || ||Not cosmopolitan|| || |
|47||Kentish plover||Not cosmopolitan|| || ||Not cosmopolitan|| || |
|48||Tern**||Core Sterna||513||13||Core Sterna, Chlidonias||633||17|
|49||Gull||Core Larus||519||31||Larus s. lat.||612||45|
|50||Curlew||Not cosmopolitan|| || ||Not cosmopolitan|| || |
|51||Snipe||Gallinago gallinago superspecies||512||2|| Gallinago ||647||16|
|52||Stint****||Core Calidris s. str.||500||6||Core Calidris s. lat.||611||10|
|53||Common sandpiper|| Actitis ||701||2||As for (b)|| || |
|54||Greenshank****||Tringa nebularia group||555||2||Not cosmopolitan|| || |
|55||Redshank||Tringa totanus group||625||5||As for (b)|| || |
|56||Green sandpiper****|| Tringa ochropus ||501||2||Not cosmopolitan|| || |
|57||Osprey||Pandionidae||571||1||Not cosmopolitan|| || |
|58||Golden eagle||Core Aquila, Hieraeetus||518||15||Aquila, Hieraeetus, Oroaetus, Spizaetus, Stephanoaetus||602||29|
|59||Kite**||Milvinae, Haliaeetinae||541||16||Milvinae, Haliaeetinae, Butastur, Bursarellus, Geranospiza||658||26|
|60||Buzzard||Core Buteo||540||13|| Buteo, Leucopternis ||603||32|
|61||Harrier||Core Circus||618||13||As for (b)||618||13|
|62||Hawk*||Accipiter s. str., Astur, Cooperastur||541||15||Accipiter s. str., Astur, Cooperastur, Leucospiza, Urospiza, Paraspizias||658||33|
|63||Barn owl****|| Tyto ||513||15||Not cosmopolitan|| || |
|64||Little owl||Surniini, Athenini||543||34||Not cosmopolitan|| || |
|65||Tawny owl||Asionini||526||8||Not cosmopolitan|| || |
|66||Eagle owl||Bubonini||528||21||Bubonini, Strigini||642||42|
|67||Kingfisher****||Cerylidae, Alcionidae||582||70||Cerylidae, Alcionidae, Alcedinidae||684||95|
|68||Spotted woodpecker||Dendropicini||587||109||Core Picinae||616||177|
|69||Green woodpecker*||Picini, Malarpicini||545||61||Included in above|| || |
|70||Falcon||Falco subbuteo group, F. columbarius||616||11||As for (b)||616||11|
|71||Peregrine|| Falco peregrinus ||559||1||Falco peregrinus and relatives||634||5|
|72||Crow*||Core Corvus||597||39||Core Corvidae||691||103|
|73||Wren****||Polioptilidae, Certhiidae, Sittidae, Troglodytidae||502||124||Not cosmopolitan|| || |
|74||Starling||Mimidae, Sturnidae, Rhabdornitidae||611||145||As for (b)||611||145|
|75||Thrush||Core Turdus||607||62||As for (b)||607||62|
|76||Bunting||Emberizidae||562||145||Not cosmopolitan|| || |
|77||Chaffinch||Fringillidae||504||135||Not cosmopolitan|| || |
|78||Pipit|| Anthus ||613||40||As for (b)||613||40|
|79||Lark||Alaudidae||513||93||Not cosmopolitan|| || |
|80||Sedge warbler****||Acrocephalidae, Megaluridae, Bernieridae, Donacobiidae||517||109||Not cosmopolitan|| || |
|81||Willow warbler****||Phylloscopidae, Sylviidae, Zosteropidae, Paradoxornithidae, Timaliidae, Aegithalidae, Cettiidae||533||520||Not cosmopolitan|| || |
|82||Barn swallow|| Hirundo rustica ||614||1||As for (b)||614||1|
|83||Red-rumped swallow*|| Cecropis, Petrochelidon ||578||14||Not cosmopolitan|| || |
Figure 1. Phylogeny of the tetrapod vertebrates indicating the least inclusive lineages with cosmopolitan terrestrial distributions, according to at least one of three criteria (a–c) (light grey, one criterion; dark grey, two criteria; black, all three criteria). Criterion (a), present in at least 215 of 281 global equal-area cells that contain at least 10% land; criterion (b), present in at least 500, or for criterion (c) at least 600, of 821 global ecoregions delimited by Olson et al. (2001). Humans and species that attained cosmopolitan status as a result of human agency were excluded. Numbers correspond to those in Table 1, where names are provided. Reference details are provided in Appendix S1.
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Among these lineages, there were clear cases of both environmental and historical limitations to colonizing the unoccupied parts of the world [biomes and regions, respectively, in Fig. 2, based on criterion (c)]. Cosmopolitan lineages, according to both criterion (b) and criterion (c), were few in number in tundra and island ecoregions but numerous elsewhere, and most numerous in southern China and northern Indochina, where four ecoregions had representatives of all the cosmopolitan lineages listed here. The number of cosmopolitan lineages was also high in the savanna and temperate forest ecoregions of the Old World, and comparatively lower in tropical rain forest and in the New World. In agreement with predictions from dispersal theory, there was indeed a paucity of cosmopolitan lineages in historically isolated regions such as Madagascar and Australia [30–40 out of 77 lineages according to criterion (b) through much of Australia; Fig. 3a,b].
Figure 2. Maps exemplifying historical and environmental limits to the natural distributions of cosmopolitan lineages (present in at least 600 of 821 global ecoregions delimited by Olson et al., 2001). (a) All regions except some island regions (mouse lineage); (b) all regions except Australia and island regions (deer lineage); (c) all biomes except cold and cool northern biomes (chameleon lineage); (d) all biomes except tundra and desert (green woodpecker lineage; also regionally absent in Australia and some island regions); and (e) all biomes except rain forest (lark lineage; also regionally absent in South America). Lineages were defined as the minimum-spanning clades that meet the 500-ecoregion criterion for being considered cosmopolitan (see text); as such, lineages are not strictly equivalent to the meaning of the corresponding English common name (e.g. chameleon lineage also includes Agamidae and Iguanidae; mouse lineage excludes some African and Madagascan representatives of Muridae s. lat.).
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Figure 3. Patterns in cosmopolitan lineage diversity and origination for terrestrial tetrapod vertebrates globally: (a, b) global patterns in the number of cosmopolitan lineages present; (c, d) the percentage of all species present belonging to cosmopolitan lineages; (e, f) the number of lineages present that are sister to cosmopolitan lineages; and (g, h) the diversity of range-restricted lineages that are sister to cosmopolitan lineages (see Materials and Methods for details). The 500-ecoregion criterion for considering a lineage cosmopolitan was employed in panels (a), (c), (e) and (g), and the 600-ecoregion criterion in panels (b), (d), (f) and (h). The six colour shades, from yellow (through green) to blue, represent the six categories in a typical box-and-whisker plot (i.e. top outliers, top whiskers, top quartile to median, median to bottom quartile, bottom whiskers, and bottom outliers, respectively).
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The percentage of species belonging to cosmopolitan lineages was variable on islands (with both very high and very low values, more often high in ecoregions comprising young isolated islands) and in arctic regions, high in desert and grassland regions (both in the Old World and in North America) and in some rain forest areas [e.g. 29.3% based on criterion (c) in the Borneo montane rain forest ecoregion], but low in Australia and South America [lowest mainland values: 11.8% according to criterion (b) in the Purus–Madeira moist forest ecoregion, and 7.9% in the Gibson Desert ecoregion according to criterion (c)]. High values were noted in cold northern ecoregions and in Southeast Asia, especially when employing criterion (b) (cf. Fig. 3c,d).
Lineages sister to cosmopolitan lineages were also concentrated in the Old World [using criterion (b); maximum value in the South China–Vietnam subtropical evergreen forest ecoregion, where there are representatives of 44 of the 77 lineages recognized based on this criterion], but were also present in the Americas, and proportionally more numerous there when employing criterion (c) (Fig. 3e,f). However, in the case of criterion (c), more of the sister lineages are cosmopolitan themselves, or are at least widespread. Low values according to both criteria were noted in arctic and island regions, and in Australia. When focusing on range-restricted lineages, the unweighted map tended to overemphasize ecoregions that have single-species narrow endemic sister lineages, while the log-transformation evened out values to the point where patterns were lost (data not presented). We present here the square-root transformation for weighted values; the absolute numbers of range-restricted lineages showed a similar pattern (not presented). In the square-root-transformed data, the areas with most range-restricted sister lineages were located in the savanna regions of Africa (Fig. 3g,h).
When employing criterion (c) (Fig. 3h), the greatest proportional contribution was made by the Kurrichane thrush (Turdus libonyanus, the senior partner in a two-species lineage sister to the cosmopolitan thrush lineage), the giraffe family (Giraffidae, probably sister to the cosmopolitan deer lineage, which also incorporates Bovidae), the honey badger (Mellivora capensis, sister to the weasel–otter lineage) and the Nesomyinae + Petromyscinae rodents (sister to the cosmopolitan mouse lineage), all of which are African endemic lineages or nearly so. When employing criterion (b), there was also a high representation of such lineages in East and Southeast Asia (Fig. 3g), and lineages (nearly) endemic to this area that contributed substantially to weighted values included wren-babblers (Pnoepyga, sister to the cosmopolitan sedge warbler lineage), the ibisbill (Ibidorhyncha struthersii, sister to the cosmopolitan stilt lineage), the Baikal teal (Anas formosa, sister to the cosmopolitan shoveller lineage), a basal squirrel lineage (Ratufa, together with Sciurillus, sister to all other squirrels), and a snake lineage (Ahaetulla + Dendrelaphis + Chrysopelea, sister to the smooth snake lineage). African lineages that contributed substantially to these values under criterion (b) were mostly distinct from those under criterion (c), including only the giraffe lineage in common, with the other lineages being the African black duck (Anas sparsa, sister to the mallard lineage), the white-faced owls (Ptilopsis, sister to tawny owls), cordyloid lizards (sister to the skink lineage) and the longclaws (Macronyx + Tmetothylacus, sister to the pipit lineage) (see references in Appendix S1). With criterion (c), values in East and Southeast Asia are lower, and values comparable to these are encountered in South America (Fig. 3h).
Cosmopolitan lineages with higher body mass and the ability to fly were represented by significantly fewer species (ANOVA and t-test respectively, P < 0.001 in both cases; see Fig. 4 for a visual representation of the differences).
Figure 4. The influence of (a) flight ability and (b) body size on the number of terrestrial tetrapod vertebrate species required to make a lineage cosmopolitan (present in at least 500 of 821 global ecoregions delimited by Olson et al., 2001).
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