Meeting Abstract

130.4  Tuesday, Jan. 7 14:15  The effect of parity (oviparous vs. viviparous) on morphological evolution among Phrynosomatidae OUFIERO, C.E.*; GARTNER, G.E.A.; Towson University; Museum of Comparative Zoology coufiero@towson.edu

A major transition in life-history evolution is the shift from egg-laying (oviparity) to live birth (viviparity). Viviparity has evolved independently multiple times among vertebrate taxa, with an estimated 100 transitions among squamates alone. Shifts in the mode of reproduction are often accompanied by changes in reproductive physiology and anatomy. Less well-studied are evolutionary consequences of changing reproductive mode on aspects of the body plan not directly related to reproduction. For instance, retention of eggs to produce live young has been proposed to affect locomotor abilities, while the production of eggs may impose certain physical constraints on the pelvic girdle. We therefore might expect that the transition from oviparity to viviparity will affect evolutionary rates of diversification for certain functionally relevant morphological traits. We tested the effect of parity on the evolution of morphological diversity in 108 species of North and Central American phrynosomatid lizards–which have an estimated six independent transitions to viviparity–by examining phylogenetically size corrected pelvic, limb and head traits. After mapping parity mode transitions to a recent, time calibrated phylogeny with SIMMAP software, we compared seven evolutionary models that vary in their parameter estimation and mode of evolution for each trait across a sample of SIMMAP trees using the OUwie package in R. Preliminary results suggest that an Ornstein-Uhlenbeck evolutionary model best explains the data often with separate optima for the two reproductive modes. Further, for some traits, viviparous species tend to have increased diversification suggesting physical constraints related to egg laying may limit morphological evolution.