MHC-based patterns of social and extra-pair mate choice in the Seychelles warbler

Abstract

The existence and nature of indirect genetic benefits to mate choice remain contentious. Major histocompatibility complex (MHC) genes, which play a vital role in determining pathogen resistance in vertebrates, may be the link between mate choice and the genetic inheritance of vigour in offspring. Studies have shown that MHC-dependent mate choice can occur in mammal and fish species, but little work has focused on the role of the MHC in birds. We tested for MHC-dependent mating patterns in the Seychelles warbler (Acrocephalus sechellensis). There was no influence of MHC class I exon 3 variation on the choice of social mate. However, females were more likely to obtain extra-pair paternity (EPP) when their social mate had low MHC diversity, and the MHC diversity of the extra-pair male was significantly higher than that of the cuckolded male. There was no evidence that females were mating disassortatively, or that they preferred males with an intermediate number of MHC bands. Overall, the results are consistent with the 'good genes' rather than the 'genetic compatibility' hypothesis. As female choice will result in offspring of higher MHC diversity, MHC-dependent EPP may provide indirect benefits in the Seychelles warbler if survival is positively linked to MHC diversity.

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

“…The parentage data allowed us to consider whether MHC similarity between mates might drive extra-pair matings, as seen in Seychelles warblers [7,22]. Previous work has shown that extra-pair fertilizations are rare in seabirds generally [65] and in this population of frigatebirds, in particular [45], so the scope for MHC to influence paternity is somewhat limited here.…”

“…Third, patterns of mate choice can be clouded by extrapair parentage, particularly in birds [44]. For example, MHC does not influence social mate choice in Seychelles warblers, but females are more likely to seek extra-pair matings if socially paired to a male with low MHC diversity [22], and these extra-pair matings confer an MHCmediated survival advantage upon offspring [7]. Thus, studies of MHC and mate choice need to be accompanied by parentage information.…”

“…Whereas a good genes process predicts that all females in the local breeding pool prefer either males with certain genotypes [12,14] or males that are heterozygous [22,23], the genetic compatibility mechanism is driven by whether a particular male's MHC genotype is a good fit for, or sufficiently different from, that of a particular female [24 -26]. The choice of a genetically compatible mate should yield MHC-heterozygous offspring that can mount an effective immune response to a wider array of pathogens [19,20].…”

Sexual selection and the evolutionary dynamics of the major histocompatibility complex

“…B 281: 20141662 diversities maintained at MHC loci. Long-term datasets including detailed pedigree information [27] may be particularly useful in testing model predictions and exploring the interaction of natural and sexual selection in shaping MHC diversity in wild populations. Our model is the first to address how discrete phases of survival and reproduction can interact to shape patterns of MHC variation, but models only one form of sexual selection, and does not yet incorporate higher-level factors, which may also contribute to immune gene variation in natural systems.…”

Breeding system and cuckoldry in the Eurasian penduline tit (Remiz pendulinus)

“…Mating with genetically dissimilar males means an increased heterozygosity of the offspring, which leads to a better immune defence (MHC-complex, Richardson et al 2005, Kempenaers 2007) and a higher success by finding a mate (genetic compatibility, Kempenaers 2007).…”