Meeting Abstract

P1-30  Saturday, Jan. 4  Male body size evolves more rapidly than female body size GHIONE, C*; LOUGH-STEVENS, M; DEAN, M; University of Southern California; University of Southern California; University of Southern Caliornia; University of Southern California; University of Southern California; University of Southern California; University of Southern California ghione@usc.edu

In mammals, males are often bigger than females leading to body size dimorphism (BSD). BSD might arise because big males acquire more mates while females are more constrained due to ecological factors. This leads to the prediction that male body size changes more rapidly over evolutionary time. Body mass data was collected for seven orders of mammals and nineteen orders of birds from multiple online databases as well as published books about body mass. Ancestral data was reconstructed using the ratebytree function of phytools. Rate shifts along the phylogenetic tree were also analyzed using BAMM and BAMMtools. In 4/6 species, male body mass changed more over the same period of evolutionary time. Rate shift analysis shows that there were more body size rate changes for males across the phylogeny. Interestingly, not all rate changes occur in the same nodes of the tree between males and females. Our analysis points to males being less constrained and able to change their body size more rapidly compared to females.