Biotic interchange has structured Western Hemisphere mammal communities

Abstract

Aim Many hypotheses posit that species‐rich tropical communities are dominated by species–species interactions, apparent as competitive exclusion or character displacement, whereas species‐poor temperate communities are dominated by species–environment interactions. Recent studies demonstrate a strong influence of macroevolutionary and biogeographical factors. We simultaneously test for the effects of species interactions, climate and biotic interchange on Western Hemisphere mammal communities using a phylogenetic and functional diversity approach. Location Western Hemisphere. Time period Modern. Major taxa studied Mammalia. Methods Using Western Hemisphere mammal distributional and body mass data, we calculate body mass dispersion, phylogenetic diversity (Net Relatedness Index) and assemblage‐averaged rates of co‐occurrence (Checkerboard scores) in 100 km × 100 km grid cells under an equal area projection. We model body mass dispersion as a function of phylogenetic diversity, co‐occurrence rates and species richness, as well as mean annual temperature and precipitation. We infer rates of dispersal among the temperate and tropical zones of the Western Hemisphere using phylogenetic methods. Results The dispersion of northern temperate mammal body masses is higher than null communities and shows correlated change with climate, consistent with resource competition and environmental filtering. Conversely, the dispersions of tropical and southern temperate mammal body masses are lower than and not differentiable from null expectations, respectively, suggesting a limited role of species–species and species–environment interactions at the grain of our analysis. Low tropical body mass dispersion and phylogenetic evenness are best explained by the high rates of faunal mixing. High rates of dispersal might also explain the similarity in community structure between the southern temperate and tropical zones. Main conclusions Mammal community assembly processes differ among the temperate and tropical zones of the Western Hemisphere, and faunal mixture during dispersal events, such as the Great American Biotic Interchange (Pliocene c. 3 Ma), may have been important in structuring Western Hemisphere mammal communities.

Divergent trends in functional and phylogenetic structure in reptile communities across Africa

“…A combination of body size and lifestyle was chosen to define the functional groupings for the present study, because we hypothesise that squamates with a similar body size and a similar lifestyle compete more strongly with each other than taxa of different sizes and ecologies. In addition, data on lifestyle and body size are among the best sampled traits across Squamata, and especially body size is often used as a proxy for functional diversity 64 , 65 . However, we acknowledge that depending on size and lifestyle, squamate species might also compete with non-squamate taxa such as mammals or birds, potentially influencing patterns within squamates.…”

Phylogenetic signal in tooth wear dietary niche proxies

“…If PNC is the rule, over evolutionary time, the Eltonian niches of closely related species should remain similar. Evolutionary conservatism has been observed for traits that are highly correlated with species’ trophic niches, including body size (Fraser & Lyons, ; Perez‐Barberia & Gordon, , ; Pineda‐Munoz, Evans, & Alroy, ; Smith et al., ) and some estimates of trophic level (Olalla‐Tárraga et al., ). Furthermore, rates of evolutionary transition among trophic levels (i.e., omnivore, herbivore, and carnivore) are asymmetric and low, implying reduced dietary lability over evolutionary time, especially among herbivores and carnivores (Price, Hopkins, Smith, & Roth, ).…”

Mammal Community Structure through the Paleocene-Eocene Thermal Maximum

“…Typically, the turnover component (often referred to as β diversity) is measured as an average difference in species composition among sites using one of a variety of dissimilarity metrics (Baselga 2010, Qian andXiao 2012) and is highest when environmental gradients are steep (Buckley and Jetz 2008). The functional (i.e., trait) and phylogenetic components of diversity are measures of niche space division that have been variously related to climate (Eronen et al 2010a, Eronen et al 2010b, Polly 2010, Qian et al 2013, Fraser and Lyons 2017, competitive interactions (Schoener 1974, Connor and Simberloff 1979, Mayfield and Levine 2010, Safi et al 2011, Fraser and Lyons 2017), speciation and extinction dynamics (Huang et al 2011, Razafindratsima et al 2012, Fraser et al 2015, and biogeographic history Lyons 2017, Lawing et al 2017). Traits, e.g., body mass, locomotor strategy, and diet, are most often used as proxies for the functional role of a species in a community (Oliveira et al 2016).…”

“…Today, communities with the most species, typically those found in the tropics, are characterized by patterns of high taxonomic turnover among communities, phylogenetic evenness (the exclusion of closely-related species from the same community), and ecological redundancy. In contrast, species poor communities tend to be comprised of phylogenetically closely-related species with high morphological disparity and little taxonomic turnover from one community to another (Buckley and Jetz 2008, Safi et al 2011, Oliveira et al 2016, Fraser and Lyons 2017. The differences in community assembly among species rich and species poor communities appear to relate to differences in climate (insofar as climate impacts the energy available to species), rates of species immigration, and rates of resource competition (Buckley and Jetz 2008, Safi et al 2011, Oliveira et al 2016, Fraser and Lyons 2017.…”

“…In contrast, species poor communities tend to be comprised of phylogenetically closely-related species with high morphological disparity and little taxonomic turnover from one community to another (Buckley and Jetz 2008, Safi et al 2011, Oliveira et al 2016, Fraser and Lyons 2017. The differences in community assembly among species rich and species poor communities appear to relate to differences in climate (insofar as climate impacts the energy available to species), rates of species immigration, and rates of resource competition (Buckley and Jetz 2008, Safi et al 2011, Oliveira et al 2016, Fraser and Lyons 2017. Making a space-for-time substitution, we predict that the rapid warming, species immigration, and increasing species richness that typified the PETM led the structure of mammal assemblages to more closely resemble modern, species rich communities, such as those in the neotropics.…”