Meeting Abstract

44.2  Saturday, Jan. 5  Endocrine-Mediated Evolution of Life History Traits: A Study of IGF-1 and Population Divergence in the Garter Snake Thamnophis elegans SPARKMAN, A.M.*; BRONIKOWSKI, A.M.; Iowa State University, Ames; Iowa State University, Ames asparkma@iastate.edu

The endocrine system is critically involved in the control of life history traits that underlie evolutionary fitness, and individual hormones may have pleiotropic effects, creating a mechanism for the evolution of correlated traits. My research tests for an endocrinological basis for intraspecific divergence of two ecotypes of the garter snake Thamnophis elegans in Eagle Lake, California, which derive from the same ancestral source population, but have evolved genetically distinct life history characteristics. Snakes from replicate meadow populations exhibit slower growth rates, lower annual reproductive output, and longer median lifespans relative to their lakeshore counterparts. Insulin-like growth factor-1 (IGF-1) is a hormone well known to promote growth and reproduction that has also been implicated in reduction of lifespan. Therefore, I hypothesize a differentiation in IGF-1 levels that could account for increased growth and reproduction and reduced survival in lakeshore versus meadow ecotypes. Here I present results from two field seasons testing IGF-1 levels in free-ranging snakes, as well as results from a year-long common garden experiment.