Diet, ecology, and dental morphology in terrestrial mammals

Dietary inferences are a key foundation for paleoecological, ecomorphological and macroevolutionary studies because they inform us about the direct relationships between the components of an ecosystem. Thus, the first part of my thesis involved creating a statistically based diet classification based on a literature compilation of stomach content data for 139 terrestrial mammals. I observed that diet is far more complex than a traditional herbivore-omnivore-carnivore classification, which masks important feeding specializations. To solve this problem I proposed a new classification scheme that emphasizes the primary resource in a given diet (Chapter 3). This new classification was then contrasted with body mass (Chapter 4). I observed that there is a specific optimum body mass range for every dietary specialization, with the medium size range mostly composed of frugivorous species that inhabit tropical and subtropical rainforests. Thus, the near absence of medium-sized mammals in open environments can be linked to the decreasing density of fruit trees needed to support a pure frugivorous diet all year round. I then evaluated previous dietary proxies and observed that a relevant time scale needs to be determined before choosing a dietary proxy (Chapter 5). The main goal of my PhD research was to design quantitative and phylogeny-free method to infer the typical diet of each species. I therefore designed Multi-Proxy Dental Morphology Analysis (MPDMA) (Chapter 6). I three dimensionally scanned thedentitions of 138 extant mammals (28 marsupials and 110 placentals) and qualitatively classified their diets. Multiple variables were estimated from the 3D scans (i.e.,orientation patch count, slope diversity, and relief index) and multivariate statistical analyses were used to test for discrimination power across dietary specializations (Chapter 7). MPDMA demonstrates significant morphological differences across diets (P < 0.05) and correctly discriminates diet for up to 82% of the specimens in the dataset. Most remarkably, marsupials and placentals with the same dietary specializations overlap strongly in ecomorphospace, which suggests convergent phenotypic evolution across both clades.