RESUMO
The zygomatic root, along with other key craniofacial features, is hypothesized to play a crucial role in strengthening the face in response to stresses and strains related to feeding. As such, it has been cited as indicative of dietary specialization among fossil taxa, although it remains unknown how variable zygomatic arch root position is among living primates, and whether its positioning predicts differences in diet. We test whether primates that consume more mechanically challenging foods possess more anteriorly positioned zygomatic roots compared to those consuming less challenging foods. Zygomatic root position, as defined by the zygomaxillare landmark, was identified and recorded from digital images and physical specimens of adult primate crania. Data were collected from 33 haplorhine species (n = 722). Published data were used to assign species to a dietary type based on patterns of overall consumption along with reliance on especially challenging foods. Pairwise comparisons between mechanically challenging (hard and/or tough) and less mechanically challenging (soft) consumers found significant differences (p < 0.05) in the position of the zygomatic root in 17 of 20 pairs, 11 of which supported the prediction that a more mechanically challenging diet is associated with a more anteriorly placed zygomatic root. PGLS analysis found no significant effect of phylogeny on root position. This suggests that a more anteriorly positioned zygomatic root is useful for identifying dietary specialization in some taxa but is not required for consuming a mechanically challenging diet given that other craniofacial and behavioral factors can facilitate the consumption of such foods.
RESUMO
Studies of the factors governing global patterns of biodiversity are key to predicting community responses to ongoing and future abiotic and biotic changes. Although most research has focused on present-day climate, a growing body of evidence indicates that modern ecological communities may be significantly shaped by paleoclimatic change and past anthropogenic factors. However, the generality of this pattern is unknown, as global analyses are lacking. Here we quantify the phylogenetic and functional trait structure of 515 tropical and subtropical large mammal communities and predict their structure from past and present climatic and anthropogenic factors. We find that the effects of Quaternary paleoclimatic change are strongest in the Afrotropics, with communities in the Indomalayan realm showing mixed effects of modern climate and paleoclimate. Malagasy communities are poorly predicted by any single factor, likely due to the atypical history of the island compared with continental regions. Neotropical communities are mainly codetermined by modern climate and prehistoric and historical human impacts. Overall, our results indicate that the factors governing tropical and subtropical mammalian biodiversity are complex, with the importance of past and present factors varying based on the divergent histories of the world's biogeographic realms and their native biotas. Consideration of the evolutionary and ecological legacies of both the recent and ancient past are key to understanding the forces shaping global patterns of present-day biodiversity and its response to ongoing and future abiotic and biotic changes in the 21st century.
