Differences in sperm traits associated to sperm competition between rodent natural populations

TOURMENTE, MAXIMILIANO; LUQUE-LARENA, JUAN JOSÉ; ROLDAN, EDUARDO R. S.

Lisboa

Conferencia; 14th Rodents et Spatium; 2014

Rodents et Spatium Consortium

Sexual selection may promote divergence in reproductive traits between populations. Sperm competition, one form of post-copulatory sexual selection, is known to favour changes in ejaculate quality and sperm swimming speed, which improve ejaculate competitiveness. We thus tested the prediction that natural populations from species with high levels of sperm competition should diverge to a greater extent in ejaculate traits than those from species with low levels of sperm competition. We compared populations of two rodent species with different sperm competition levels. Our results showed that populations from a species with high levels of sperm competition (Apodemus sylvaticus) exhibited differences in relative testes size, sperm quality and swimming velocity. In addition, variation within populations was small. In contrast, populations from a species with low levels of sperm competition (Mus domesticus) showed fewer differences between populations and a larger degree of variation within populations, which resulted in a substantial degree of overlap in sperm traits between populations. We conclude that sperm competition may promote divergence in sperm traits because populations tend to differ in the intensity of sexual selection, leading to different rates of evolutionary change and a small degree of variation within populations.