Meeting Abstract
Morphological innovations have been extensively discussed as drivers of lineage diversification. In this study, we examine the role of body size and shape and their effects on the evolution of musteloids. Previous work revealed musteloids exhibit decoupled diversification dynamics driven by increased clade carrying capacity in the branches leading to a subclade of mustelids as well as a lack of correspondence in patterns of body length and body mass evolutionary rates within the decoupled mustelid subclade. These results suggest that body elongation could be an innovation for the exploitation of novel Mid-Miocene resources, resulting in increased species richness of “elongate” mustelids. To further test this hypothesis, we first examined the evolution of body size in musteloids and find that small body size is associated with primarily mustelines and some gulonines and ictonychines. We then quantify body shape using the vertebrate shape index, a metric that describes a continuum of body shape from disc- or football-shaped bodies to elongate forms and allows for examination of the underlying morphological changes that can drive the evolution towards more elongate body plans. We found that mustelid crown clades Helictindinae, Martinae, Ictonychinae, Mustelinae and Lutrinae exhibited shifts towards more elongate shape optima and that weasels consistently shifted towards the most elongate optima. These results support the hypothesis that body elongation potentially served as a morphological innovation allowing weasels to specialize on subterranean rodents.
