A test for rate-coupling of trophic and cranial evolutionary dynamics in New World bats.

Morphological evolution is often assumed to be causally related to underlying patterns of ecological trait evolution. However, few studies have directly tested whether evolutionary dynamics of-and major shifts in-ecological resource use are coupled with morphological shifts that may facilitate trophic innovation. Using diet and multivariate cranial (microCT) data, we tested whether rates of trophic and cranial evolution are coupled in the radiation of New World bats. We developed a generalizable information-theoretic method for describing evolutionary rate heterogeneity across large candidate sets of multirate evolutionary models, without relying on a single best-fitting model. We found considerable variation in trophic evolutionary dynamics, in sharp contrast to a largely homogeneous cranial evolutionary process. This dichotomy is surprising given established functional associations between overall skull morphology and trophic ecology. We suggest that assigning discrete trophic states may underestimate trophic generalism and opportunism, and that this radiation could be characterized by labile crania and a homogeneous dynamic of generally high morphological rates. Overall, we discuss how trophic classifications could substantively impact our interpretation of how these dynamics covary in adaptive radiations.

Digitizing extant bat diversity: An open-access repository of 3D µCT-scanned skulls for research and education.

Biological specimens are primary records of organismal ecology and history. As such, museum collections are invaluable repositories for testing ecological and evolutionary hypotheses across the tree of life. Digitizing and broadly sharing the phenotypic data from these collections serves to expand the traditional reach of museums, enabling widespread data sharing, collaboration, and education at an unprecedented scale. In recent years, µCT-scanning has been adopted as one way for efficiently digitizing museum specimens. Here, we describe a large repository of 3D, µCT-scanned images and surfaces of skulls from 359 extant species of bats, a highly diverse clade of modern vertebrates. This digital repository spans much of the taxonomic, biogeographic, and morphological diversity present across bats. All data have been published to the MorphoSource platform, an online database explicitly designed for the archiving of 3D morphological data. We demonstrate one potential use of this repository by testing for convergence in skull shape among one particularly diverse group of bats, the superfamily Noctilionoidea. Beyond its intrinsic utility to bat biologists, our digital specimens represent a resource for educators and for any researchers seeking to broadly test theories of trait evolution, functional ecology, and community assembly.

Speciation dynamics during the global radiation of extant bats.

Species richness varies widely across extant clades, but the causes of this variation remain poorly understood. We investigate the role of diversification rate heterogeneity in shaping patterns of diversity across families of extant bats. To provide a robust framework for macroevolutionary inference, we assemble a time-calibrated, species-level phylogeny using a supermatrix of mitochondrial and nuclear sequence data. We analyze the phylogeny using a Bayesian method for modeling complex evolutionary dynamics. Surprisingly, we find that variation in family richness can largely be explained without invoking heterogeneous diversification dynamics. We document only a single well-supported shift in diversification dynamics across bats, occurring at the base of the subfamily Stenodermatinae. Bat diversity is phylogenetically imbalanced, but-contrary to previous hypotheses-this pattern is unexplained by any simple patterns of diversification rate heterogeneity. This discordance may indicate that diversification dynamics are more complex than can be captured using the statistical tools available for modeling data at this scale. We infer that bats as a whole are almost entirely united into one macroevolutionary cohort, with decelerating speciation through time. There is also a significant relationship between clade age and richness, suggesting that global bat diversity may still be expanding.