Sequence-based evidence for major histocompatibility complex-disassortative mating in a colonial seabird

Abstract

The major histocompatibility complex (MHC) is a polymorphic gene family associated with immune defence, and it can play a role in mate choice. Under the genetic compatibility hypothesis, females choose mates that differ genetically from their own MHC genotypes, avoiding inbreeding and/or enhancing the immunocompetence of their offspring. We tested this hypothesis of disassortative mating based on MHC genotypes in a population of great frigatebirds (Fregata minor) by sequencing the second exon of MHC class II B. Extensive haploid cloning yielded two to four alleles per individual, suggesting the amplification of two genes. MHC similarity between mates was not significantly different between pairs that did (n ¼ 4) or did not (n ¼ 42) exhibit extra-pair paternity. Comparing all 46 mated pairs to a distribution based on randomized re-pairings, we observed the following (i): no evidence for mate choice based on maximal or intermediate levels of MHC allele sharing (ii), significantly disassortative mating based on similarity of MHC amino acid sequences, and (iii) no evidence for mate choice based on microsatellite alleles, as measured by either allele sharing or similarity in allele size. This suggests that females choose mates that differ genetically from themselves at MHC loci, but not as an inbreeding-avoidance mechanism.

Major histocompatibility complex class II compatibility, but not class I, predicts mate choice in a bird with highly developed olfaction

“…On the other hand, alternative mating strategies are found in passerines, with an increased success in extra-pair matings when the social mate is MHC similar [53 -55]. In the serial monogamous great frigatebird, Fregata minor (Pelicaniformes), a disassortative mating pattern for two MHC class II B loci was recently shown [56]. The addition of our findings, a remotely related species, may indicate that this mate choice strategy is a common feature among seabirds.…”

Social and extra-pair mating in relation to major histocompatibility complex variation in common yellowthroats

“…The most common pattern appears to be a bias towards matings between females and males that are relatively MHC-dissimilar, which occurs in mammals [18,19], fish [20,21], reptiles [22,23] and birds [24,25]. This disassortative mating at the MHC could reduce inbreeding and increase the heterozygosity of the offspring.…”

Divergent allele advantage at MHC-DRB through direct and maternal genotypic effects and its consequences for allele pool composition and mating

“…An increasing number of studies is now reporting mate preference with respect to MHC divergence [13][14][15][16][17]. Mate choice for allele divergence is in fact expected to be highly advantageous, because neither heterozygosity nor allele divergence at the MHC can directly be inherited owing to the compound nature of this trait.…”