title: The more pieces, the better the puzzle: sperm concentration increases gametic compatibility.
abstract: The genetic benefits individuals receive from mate choice have been the focus of numerous studies, with several showing support for both intrinsic genetic benefits and compatibility effects on fertilization success and offspring viability. However, the robustness of these effects have rarely been tested across an ecologically relevant environmental gradient. In particular, sperm environment is a crucial factor determining fertilization success in many species, especially those with external fertilization. Here, we test the importance of sperm environment in mediating compatibility-based selection on fertilization using a factorial breeding design. We detected a significant intrinsic male effect on fertilization success at only one of four sperm concentrations. Compatibility effects were significant at the two highest sperm concentrations and, interestingly, the magnitude of the compatibility effect consistently increased with sperm concentration. This suggests that females are able to modify the probability of sperm-egg fusion as the amount of sperm available increases.
authors.affiliation: Centre for Integrative Ecology School of Life and Environmental Sciences Deakin University Waurn Ponds Victoria 3216 Australia.
authors.forename: Craig D H
authors.initials: CD
authors.lastname: Sherman
authors.affiliation: Centre for Integrative Ecology School of Life and Environmental Sciences Deakin University Waurn Ponds Victoria 3216 Australia ; School of Biological Sciences Universiti Sains Malaysia 11800 Minden Penang Malaysia.
authors.forename: Emi S
authors.initials: ES
authors.lastname: Ab Rahim
authors.affiliation: School of Biological Sciences The University of Sydney Sydney New South Wales 2006 Australia.
authors.forename: Mats
authors.initials: M
authors.lastname: Olsson
authors.affiliation: Centre for Integrative Ecology School of Life and Environmental Sciences Deakin University Waurn Ponds Victoria 3216 Australia.
authors.forename: Vincent
authors.initials: V
authors.lastname: Careau
keywords: Cryptic female choice; Mytilus; genotype by environment; good genes; polyandry; quantitative genetics; sperm competition