WHAT DRIVES RANGE SIZE VARIATION?

Understanding the driving forces behind variation in range size is crucial to conservation efforts in a world where habitats are rapidly changing and becoming increasingly fragmented due to human intervention. To better understand variation in species range sizes, we must identify the behavioral, morphological, and ecological characteristics that influence it. Doing so will shed light on the causes of variation in geographic distribution, and thus, chances of species survival. Here, we tested the effects of ecology, morphology, and social behaviors on range size. We used the carnivoran super-family Musteloidea (which includes badgers, otters, raccoons, weasels, and red pandas) as our model clade because of its nearly global distribution and large variance in body shapes, lifestyles, and social behaviors. We predicted that body mass, diet type, and social behavior would all have a deterministic effect on range area. Contrary to our prediction, the phylogenetic ANOVA revealed that body mass, social grouping, diet type, head to body elongation ratio, and cranial size did not have a significant effect on species range, with habitat type revealing significant differences only between marine and terrestrial aquatic species, and cranial shape exhibiting a weak correlation. These results reaffirm the complexity of species range, and suggests that within this group, no single metric is able to explain the large variation in species distribution. However, the presence of a significant relationship between at least one axis of cranial morphometric variation and species range suggests a relationship between jaw geometry and adaptability potentially as a result of increased jaw musculature and thus greater bite force. Furthermore, we suggest directions for future study through the examination of the effects of locomotion, sexual dimorphism, and individual territorial ranges on species range size.