Meeting Abstract

1.7  Jan. 4  A phylogenetic analysis of scale variation in the lizard genus Sceloporus ADOLPH, S.C.; GARTNER, G.E.A.; OUFIERO, C.E.*; GARLAND, T.; Harvey Mudd College, Claremont CA; Univ. of California, Riverside; Univ. of California, Riverside; Univ. of California, Riverside ggart001@ucr.edu

Although the general function of reptilian scales is well understood, the functional significance of variation in scale size and morphology is less clear. Scale size and number vary both within and among species of squamates, and scale counts have been extensively used as taxonomic and phylogenetic characters in lizards and snakes. Studies have explored the potential adaptive significance of variation in scale size and number and have typically focused on possible climatic correlates of scale size variation (e.g., environmental temperature). Here we examine the hypothesis, from Soul� (1966) and Regal (1975), that smaller scales (manifested as more scale rows) should be advantageous in colder climates (e.g., at higher latitudes) to aid in heat retention whereas fewer scale rows (larger scales) will evolve in warmer environments to aid in heat dissipation. We gathered data on snout-vent length, number of dorsal scale rows, number of femoral pores, and latitude (as a surrogate for temperature) from the literature and museum specimens for 106 species/populations of Sceloporus lizards, and analyzed the data with phylogenetically based statistical methods. Mean number of dorsal scale rows ranged from 27 to 88, which is almost certainly far greater than could be caused by direct environmental effects alone (i.e., phenotypic plasticity). Some of the variation in scale rows was related to body size, with larger-bodied species having fewer scale rows, and thus by implication larger scales. After adjusting for the correlation with SVL, number of scale rows had highly significant phylogenetic signal (P << 0.001, K = 0.726). In a multiple regression with independent contrasts, the effect of SVL remained negative and statistically significant, and the effect of latitude was positive and also significant, which is consistent with the Soul�-Regal hypothesis.