Testing links between species traits, phylogeny and environment in a Mojave Desert rodent metacommunity

Background/Question/Methods

Elucidating mechanisms that determine species distribution and abundance is a fundamental concern of ecology. At local to regional spatial scales, environment (rather than climate) is known to strongly influence species occurrence. These effects are often attributed to trait differences between species. However, direct links between species traits, phylogeny, and species distribution in heterogeneous environments have rarely been tested. Here we analyze these relationships in a Mojave Desert rodent metacommunity containing 13 species distributed across 31 sites. Rodent abundance was sampled between September and November 2005 using Sherman traps and abundance data were square-root transformed to reduce the influence of the most abundant species. We used an extension of the fourth corner method to test for linkages between environmental variables (macrohabitat type, 8 PC axes based on biomass of 81 plant species, and 2 PC axes based on 9 soil and rock classes), species traits (morphometric variables, mode of locomotion, feeding guild, and life history traits) and phylogeny (phylogenetic tree of all nocturnal Mojave Desert rodents trimmed to include only species present across sampled communities). 

Results/Conclusions

Using the fourth corner method, preliminary results suggest a significant relationship between species occurrence and microhabitat (P < 0.001) and between species occurrence and morphometric variables (P = 0.177). Hence, species traits and environment are significantly linked through species occurrence. Of all species traits, morphometric variables were most closely associated with microhabitat variables. In addition, microhabitat variables were significantly correlated with differences in species occurrence within nodes, with perennial plant diversity accounting for most of the significant links between phylogeny and environment. These results suggest that environmental variation between habitats plays an important role in local community structure of Mojave Desert rodents and this response is mediated by species traits.