Data from: Hybridization, reinforcement selection and sex-dependent reproductive character displacement of sperm and egg recognition proteins

The establishment of reproductive isolation between species via gametic
incompatibility initially requires within-species selection for variation
in reproductive compatibility. We investigate how the generation of
within-species variation in sperm and egg recognition proteins,
potentially via sexual conflict, influences reproductive isolation between
two partially sympatric sea urchin species; the North American west coast
Mesocentrotus franciscanus and the circumpolar Strongylocentrotus
droebachiensis. Barriers to hybridization are stronger when eggs are given
a choice of conspecific versus heterospecific sperm and the variation in
hybridization among crosses can be explained by whether the sperm or egg
protein variant is ancestral or derived. Derived proteins can be
recognized as different and prevent hybridization. Examination of the
allele frequencies of these proteins in M. franciscanus in and out of
sympatry with S. droebachiensis along the west coast of North America
reveals evidence of reinforcement selection and reproductive character
displacement in eggs but not sperm, which likely reflects the differential
cost of hybridization for males and females.