Data from: MHC class II assortative mate choice in European badgers (Meles meles)

The major histocompatibility complex (MHC) plays a crucial role in the
immune system, and in some species, it is a target by which individuals
choose mates to optimize the fitness of their offspring, potentially
mediated by olfactory cues. Under the genetic compatibility hypothesis,
individuals are predicted to choose mates with compatible MHC alleles, to
increase the fitness of their offspring. Studies of MHC-based mate choice
in wild mammals are under-represented currently, and few investigate more
than one class of MHC genes. We investigated mate choice based on the
compatibility of MHC class I and II genes in a wild population of European
badgers (Meles meles). We also investigated mate choice based on
microsatellite-derived pairwise relatedness, to attempt to distinguish
MHC-specific effects from genomewide effects. We found MHC-assortative
mating, based on MHC class II, but not class I genes. Parent pairs had
smaller MHC class II DRB amino acid distances and smaller functional
distances than expected from random pairings. When we separated the
analyses into within-group and neighbouring-group parent pairs, only
neighbouring-group pairs showed MHC-assortative mating, due to similarity
at MHC class II loci. Our randomizations showed no evidence of
genomewide-based inbreeding, based on 35 microsatellite loci; MHC class II
similarity was therefore the apparent target of mate choice. We propose
that MHC-assortative mate choice may be a local adaptation to endemic
pathogens, and this assortative mate choice may have contributed to the
low MHC genetic diversity in this population.