Tuesday, June 5, 2007

Sex-role reversal and reproductive success in the giant water bug Abedus herberti (Hemiptera: Belostomatidae)

Marshall E. Knoderbane and David A. Lytle. Department of Zoology, Oregon State University, Corvallis, OR 97331

Mode of parental care greatly influences the mating system of a species. We investigated the potential for sex-role reversal in Abedus herberti (Hemiptera: Belostomatidae), a species with paternal care of eggs. Sexual selection theory predicts that the relationship between number of matings and total offspring production (the Bateman gradient) should be steeper for the sex with lower per-offspring investment. While male fitness is limited by the number of eggs he can back-brood, females are not constrained by post-zygotic care of offspring. We used the naturally-occurring genetic marker Stripe (single autosomal dominant allele) to track the mating behavior of a single Stripe female placed into laboratory populations with equal sex ratios. After 21 days of mating and 27days of brooding the reproductive success of the Stripe female was discernable by the distribution and number of Stripe offspring per male. Females had a mean of 2.6 0.89 mates and showed increased fitness with increased number of matings?one indication of sex-role reversal. In the future, more precise genetic markers, such as microsatellites, could be used to assess whether the mating system of A. herberti demonstrates complete sex-role reversal or mutual promiscuity.