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Global desert rodent communities were examined for evidence of phylogenetic and morphological community structure. Using geographical distribution data of desert rodents (within 15 assemblages), a composite molecular phylogeny and a geometric morphometric dataset of skulls, the mean pairwise distance and mean nearest taxon distance were calculated for each assemblage and compared with null communities. Community structure metrics detected phylogenetic clumping in two out of the 15 desert assemblages, indicating that co-occurring rodents were more closely related than expected by chance. No other assemblages showed a significant phylogenetic structure. Skull morphology had different structuring patterns, but overall, most examined desert assemblages were not significantly structured in skull morphology. Similar overall lack of community structure patterns was observed at the regional scale in both the phylogenetic and the body mass datasets. We also directly tested the association between phylogenetic and morphological structure and found it to be significant. The association between phylogenetic distance and increased diversity that we observed might indicate that niche partitioning facilities coexistence in diverse assemblages. [ABSTRACT FROM AUTHOR]

Functional dental theory predicts that tooth shape responds evolutionarily to the mechanical properties of food. Most studies of mammalian teeth have focused on qualitative measures of dental anatomy and have not formally tested how the functional components of teeth adapt in response to diet. Here we generated a series of predictions for tooth morphology based on biomechanical models of food processing. We used murine rodents (Old World rats and mice) to test these predictions for the relationship between diet and morphology and to identify a suite of functional dental characteristics that best predict diets. One hundred and five dental characteristics were extracted from images of the upper and lower tooth rows and incisors for 98 species. After accounting for phylogenetic relationships, we showed that species evolving plant-dominated diets evolved deeper incisors, longer third molars, longer molar crests, blunter posteriorly angled cusps, and more expanded laterally oriented occlusal cusps than species adapting to animal-dominated diets. Measures of incisor depth, crest length, cusp angle and sharpness, occlusal cusp orientation, and the lengths of third molars proved the best predictors of dietary adaptation. Accounting for evolutionary history in a phylogenetic discriminant function analysis notably improved the classification accuracy. Molar morphology is strongly correlated with diet and we suggest that these dental traits can be used to infer diet with good accuracy for both extinct and extant murine species. [ABSTRACT FROM AUTHOR]

The emergence of exceptionally diverse clades is often attributed to ecological opportunity. For example, the exceptional diversity in the most diverse superfamily of mammals, muroid rodents, has been explained in terms of multiple independent adaptive radiations. If multiple ecological opportunity events are responsible for generating muroid diversity, we expect to find evidence of these lineages ecologically diversifying following dispersal into new biogeographical areas. In the present study, we tested the trait-based predictions of ecological opportunity using data on body size, appendages, and elevation in combination with previously published data on biogeographical transitions and a time-calibrated molecular phylogeny. We identified weak to no support of early ecological diversification following the initial colonizations of all continental regions, based on multiple tests, including node height tests, disparity through time plots, evolutionary model comparison, and Bayesian analysis of macroevolutionary mixtures. Clades identified with increased diversification rates, not associated with geographical transitions, also did not show patterns of phenotypic divergence predicted by ecological opportunity, which suggests that phylogenetic diversity and phenotypic disparity may be decoupled in muroids. These results indicate that shifts in diversification rates and biogeographically-mediated ecological opportunity are poor predictors of phenotypic diversity patterns in muroids. [ABSTRACT FROM AUTHOR]