Evidence for multiple insemination in the common garter snake, Thamnophis sirtalis

Morph frequencies in litters of naturally mated female Thamnophis sirtalis from populations containing a recessive allele for melanism were found to deviate significantly from simple Mendelian values. These deviations are attributed to multiple male parentage. It is argued that multiple insemination and the resultant sperm competition are viewed most profitably together with copulatory plugs, hemipenal morphology, and aspects of male and female reproductive behavior as consequences of intense intrasexual selection among males.