Evolutionary history, paleo- and contemporary environmental changes drive tropical mammal community structure

Background/Question/Methods

Multiple hypotheses have been proposed to explain the latitudinal diversity gradient, including evolutionary hypotheses related to time or energy stability for driving species diversification, and ecological processes promoting species co-existence. However, a single explanation from an evolutionary or ecological perspective may not be sufficient to explain the diversity disparity among tropical realms. To better understand the underlying processes driving variation in species richness throughout the tropics, we used occurrence data from 15 sites collected by the standardized camera-trap monitoring protocol of the Tropical Ecological Assessment and Monitoring Network and evaluated the relative importance of evolutionary and ecological drivers of the phylogenetic and functional structure of ground-dwelling mammal communities. Specifically, we used linear regression models to test the relative importance of colonization time, climate change and anthropogenic disturbance over geological time, and contemporary energy seasonality and environmental heterogeneity on community structure.

Results/Conclusions

We found that the general pattern of functionally clustered tropical community structure, which has been previously described as functional redundancy, has been shaped by different phylogenetic structures among tropical regions that range from clustered to dispersed. This suggests different evolutionary trajectories among tropical regions. Longer time since colonization resulted in higher extinction probabilities of some clades and speciation among closely related species, leading to phylogenetically dispersed structure at the phylogenetic tree root, but clustered structure for closely related species and for functional diversity. Greater habitat heterogeneity contributed to phylogenetically and functionally dispersed community structures potentially by providing species more opportunities to adaptively diversify for each habitat type and supporting diverse species. Contrastingly, greater temperature changes over geological time excluded intolerant clades from the tree root, and recent speciation of remaining clades contributed to phylogenetically and functionally clustering at tree tips. More potent anthropogenic disturbance over geological time and contemporary energy instability also acted as abiotic filters to exclude intolerant clades, resulting in phylogenetically dispersed but functionally clustered community structure. Our results provide insight into the evolutionary trajectories driven by evolutionary history, paleo- and contemporary environmental changes among tropical realms, shaping the phylogenetic and functional structure of contemporary tropical mammal communities.