Meeting Abstract

52.3  Sunday, Jan. 5 10:30  Interspecific and interpopulational variation in traits associated with postcopulatory sexual selection in garter snakes FRIESEN, C.R.*; MASON, R.T.; UHRIG, E.J.; BENTZ, E.; KING, R.B.; WUSTERBARTH, T.; Univ. Sydney; Oregon State Univ.; Oregon State Univ.; Oregon State Univ.; Northern Illinois Univ.; Northern Illinois Univ. christopher.friesen@sydney.edu.au

Postcopulatory sexual selection—sperm competition and cryptic female choice—is a ubiquitous mechanism of evolutionary change. Traits such as testis mass, sperm number and sperm length often vary in predictable ways among species and populations that have experienced different levels of postcopulatory selection. Garter snakes (genus Thamnophis) are a model for the study of reproductive biology and behavioral ecology. Much of the work on garter snakes has been conducted on the large mating aggregations of the Interlake region of Manitoba, Canada. We address the question: Is there evidence that the Interlake populations of red-sided garter snakes experience strong postcopulatory selection relative to congeneric species? We present sperm length data from six different species of garter snake Thamnophis, three subspecies of T. sirtalis. We also address the same question at the interpopulational level and present sperm length, sperm count and testes mass data from two different populations of the T.s.parietalis. Finally, we present data comparing total sperm numbers and a qualitative assessment of the copulatory plug in T. sirtalis and T. radix. We interpret our results in light of the vast theoretical models of sperm competition.