Meeting Abstract

P2.189  Saturday, Jan. 5  Relative brain size decreases with limb loss in squamates HEESY, C.P.*; KAMILAR, J.M.; Midwestern University; Midwestern University and Arizona State Univ. cheesy@midwestern.edu

Most variance in vertebrate brain size is explained by its relationship to body size. However, the underlying biological mechanism that relates brain to body size in vertebrates continues to be debated. One potentially valuable clade that can be used to study vertebrate brain:body size allometry is lepidosaurs (tuataras, lizards, and snakes) within which relatively large brain size has evolved multiple times among presumably distantly related lizard groups. Additionally, brain size has been suggested to be smaller in elongate, and/or limbless vertebrates, including snakes and some lizards. In this study, we examine the relationship between digit and limb loss on brain:body size scaling in lepidosaurs. We combine data on brain and body mass from multiple sources and also collate data on digit and limb number in these taxa. Lastly, we employ modern phylogenetic statistical approaches to the analysis of these data. Our analyses are consistent with the hypothesis that relative brain size decreases with digit and limb loss, and the relationship between brain:body size ratio and limb loss has evolved multiple times within lizards as well as in snakes. We also find that relative cerebellum volume decreases with digit and limb reduction and loss. Relative brain size reductions in squamates with limb loss can be interpreted as reflecting lower innervation demands by body wall structures.