Within-trio tests provide little support for post-copulatory selection on MHC haplotypes in a free-living population

Sexual selection has been proposed as a force that could maintain the diversity of major histocompatibility complex (MHC) genes in vertebrates. Potential selective mechanisms can be divided into pre-copulatory and post-copulatory, and in both cases the evidence for occurrence is mixed, especially in natural populations. In this study, we used a large number of parent-offspring trios that were diplotyped for MHC class II genes in a wild population of Soay sheep (Ovis aries) to examine whether there was within-trio post-copulatory selection on MHC genes at both the haplotype and diplotype levels. We found there was transmission ratio distortion of one the eight MHC class II haplotype (E) which was transmitted less than expected by fathers, and transmission ratio distortion of another haplotype (A) which was transmitted more than expected by chance to male offspring. However, in both cases these deviations were not significant after correction for multiple tests. In addition, we did not fi...