Mate choice among sympatric fur seals: female preference for conphenotypicmales

When closely related species breed in sympatry, and where hybrids have lowe r fitness, reinforcement theory predicts that selection should favour mecha nisms that reduce the probability of interspecific matings. If this situati on arises among species that exhibit resource defence polygyny where males and females of different species reside in the same territories, there may be some conflict between mate choice based on territory-holding ability (se xual selection) and mate choice for correct species. We investigated this i n a population of fur seals where three species are sympatric and where som e females breed in the territories of heterospecific males, and where inter specific matings and hybrid pups are observed. The territorial status of ma les and the birthing sites of females were determined during daily observat ions, as were the movements of males and females, the location of matings a nd mating partners. DNA extracted from skin samples was used to determine p aternities using DNA fingerprinting and the mtDNA genotype of individuals. Individuals were also classed on the basis of species-typical phenotype. We found that extra-territory inseminations (ETIs) were significantly more pr evalent (67%) when territorial males and resident females were of different phenotype than when of similar phenotype (27%), but mtDNA genotype had no effect on the rate of ETIs. ETIs were probably by males with the same pheno type, as pups born to these females in the following season had the same ph enotype as their mothers, suggesting they were not hybrids. These results s uggest that within the resource defence polygynous mating system of these s ympatric fur seals, female mate choice is more influenced by male phenotype than genotype. Contrary to our predictions, our study indicates that poten tial conflict between mate choice based on sexual selection and species rec ognition is unlikely, because Females have some capacity to discriminate be tween males both within and between species on phenotypic traits additional to those under sexual selection. Although at least 25% of the pups born in this study were hybrid, this study can only support reinforcement theory i f hybrids have reduced fitness. The fitness of hybrids among the species st udied is currently unknown.