MYERS, E.M.*; ZAMUDIO, K.R.; Cornell University, Ithaca, NY; Cornell University, Ithaca, NY: Genetic Characterization of Reproductive Strategy in an Amphibian with Aggregate Breeding

Aggregate or explosive breeding is widespread among vertebrates and likely increases the probability of multiple paternity. We assessed paternity in seven field collected clutches of the explosive breeding spotted salamander (Ambystoma maculatum) using ten microsatellite loci to determine the frequency of multiple paternity, the number of contributing males, and the degree of reproductive skew among contributing males to a female’s clutch. Using the Minimum Method of allele counts, multiple paternity was evident in 70% of these egg masses. We also analyzed genotype distributions using computer simulations that estimate the most likely number of contributing fathers given population allele frequencies when parental genotypes are unknown. We simulated levels of equal male contributions and two estimates of reproductive skew and determined that genotype data for a minimum of twenty to thirty offspring per clutch are needed to determine multiple parental contributions in this system . For those clutches meeting this minimum requirement we determined that between two and eight males contribute normally to A. maculatum clutches in naturally breeding populations. Estimates of reproductive skew have a significant influence on assays of the number of male contributors. These results suggest that multiple paternity is a common strategy in this species and that females may benefit from producing offspring sired by more than one male.