Sharlene E. Santana: UCLA

The rich morphological diversity of mammal faces has captured the attention of naturalists for over a century. Researchers have long proposed that social behaviors have primarily shaped the intraspecific variation and interspecific diversity in the faces of some visually-oriented groups such as primates. However, mammal faces constitute complex structures where the potentially competing functions of communication, ecology, and physiology intersect, and the major determinants of facial diversity still remain poorly understood. In this talk, I examine the relationship among facial traits, social and ecological factors within several groups of mammals. Through a phylogenetic comparative approach, I provide the first evidence for an adaptive role of facial color patterns and coloration. For primates in particular, I describe how species living in smaller groups and in high degrees of sympatry with congeners have evolved more complex patterns of facial coloration. Furthermore, the evolution of facial pigmentation and hair length is linked to ecological factors, and ecogeographical rules related to UV radiation and thermoregulation are met by some but not all facial regions. These results demonstrate the interaction between behavioral and ecological factors in shaping facial diversity across mammalian clades.