Global mammal beta diversity shows parallel assemblage structure in similar but isolated environments

Abstract

The taxonomic, phylogenetic and trait dimensions of beta diversity each provide us unique insights into the importance of historical isolation and environmental conditions in shaping global diversity. These three dimensions should, in general, be positively correlated. However, if similar environmental conditions filter species with similar trait values, then assemblages located in similar environmental conditions, but separated by large dispersal barriers, may show high taxonomic, high phylogenetic, but low trait beta diversity. Conversely, we expect lower phylogenetic diversity, but higher trait biodiversity among assemblages that are connected but are in differing environmental conditions. We calculated all pairwise comparisons of approximately 110 Â 110 km grid cells across the globe for more than 5000 mammal species (approx. 70 million comparisons). We considered realms as units representing geographical distance and historical isolation and biomes as units with similar environmental conditions. While beta diversity dimensions were generally correlated, we highlight geographical regions of decoupling among beta diversity dimensions. Our analysis shows that assemblages from tropical forests in different realms had low trait dissimilarity while phylogenetic beta diversity was significantly higher than expected, suggesting potential convergent evolution. Low trait beta diversity was surprisingly not found between isolated deserts, despite harsh environmental conditions. Overall, our results provide evidence for parallel assemblage structure of mammal assemblages driven by environmental conditions at a global scale.

Global patterns of β‐diversity along the phylogenetic time‐scale: The role of climate and plate tectonics

“…However, our results indicate that contemporary geographical distances explain β‐diversity better than climate for both birds and mammals, suggesting that, at this scale, dispersal limitations have a greater influence than climatic filtering. This is in line with the argument that, at the global scale, faunas of different continents are often very dissimilar because they have been isolated for a long time, with relatively few dispersal events (Flynn, ; Holt et al, ; Lomolino et al, ; Penone et al, ; Simpson, ). One alternative explanation is that the climatic variables used here do not perfectly describe the climatic conditions actually experienced by animals, and that geographical distances incorporate differences in additional climatic or ecological conditions that potentially constrain branches to different regions (Anderson et al, ).…”

“…These relatively fine‐scale climatic species affinities may not be conserved at deep phylogenetic scales, which might partly explain why climatic distances mainly explain species β‐diversity. Although beyond the scope of this study, an interesting avenue for future research could be to analyse correlation profiles across phylogenetic scales and climatic scales (e.g., using biomes instead of the climatic variables used here; see Penone et al, ).…”

Environmental factors explain the spatial mismatches between species richness and phylogenetic diversity of terrestrial mammals

“…Previous studies have shown that even though SR and PD are strongly correlated, the spatial patterns in mammalian SR do not account for the variation in PD, and such mismatches provide insights into ecological and evolutionary processes (Davies & Buckley, ; Penone et al, ; Safi et al, ). Here, we demonstrate that regionally structured mismatches between richness and PD of terrestrial mammals are associated with the group biogeographical history and with the different ways in which both dimensions of biodiversity relate to current and past environmental factors.…”

“…Mammals have a clear latitudinal gradient of higher SR and PD in the tropics, but the spatial patterns of each dimension are not always congruent, with some areas having more or less PD than expected based on richness alone (Davies & Buckley, ). Spatially structured differences between SR and PD reflect differences in species composition, which are likely to be influenced by environmentally driven ecological and evolutionary processes (Davies et al, ; Penone et al, ; Safi et al, ). Thus, a comparison of how SR and PD relate to each other and to environmental factors offers clues about the underlying mechanisms behind diversity patterns (Davies et al, ).…”

The Geography of Ecological Niche Evolution in Mammals

“…Species ecological niches were defined using a set of four traits (diet, body-mass, activity cycle and foraging strata) that produce a coarse representation of animal Eltonian niches [13][14][15][16]. While diet and body mass directly refer to species resource requirement, foraging location and activity represent behavioural traits reflecting how species acquire food from their environment.…”