Extra‐pair mating in a passerine bird with highly duplicated major histocompatibility complex class II: Preference for the golden mean

Genes of the major histocompatibility complex (MHC) are essential in vertebrate adaptive immunity, and they are highly diverse and duplicated in many lineages. While it is widely established that pathogen‐mediated selection maintains MHC diversity through balancing selection, the role of mate choice...

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Bibliographic Details
Published in:Molecular ecology 2019-12, Vol.28 (23), p.5133-5144
Main Authors: Rekdal, Silje L., Anmarkrud, Jarl Andreas, Lifjeld, Jan T., Johnsen, Arild
Format: Article
Language:English
Subjects:
Adaptive immunity
Animal behavior
Autoimmunity
bluethroat
compatibility
Extra-pair paternity
extra‐pair mating
Genes
Genetic diversity
Major histocompatibility complex
mate choice
Mate selection
Mating
Offspring
optimal MHC
Optimization
Paternity
Pathogens
Reproduction (copying)
Songbirds
Vertebrates
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Summary:Genes of the major histocompatibility complex (MHC) are essential in vertebrate adaptive immunity, and they are highly diverse and duplicated in many lineages. While it is widely established that pathogen‐mediated selection maintains MHC diversity through balancing selection, the role of mate choice in shaping MHC diversity is debated. Here, we investigate female mating preferences for MHC class II (MHCII) in the bluethroat (Luscinia svecica), a passerine bird with high levels of extra‐pair paternity and extremely duplicated MHCII. We genotyped family samples with mixed brood paternity and categorized their MHCII alleles according to their functional properties in peptide binding. Our results strongly indicate that females select extra‐pair males in a nonrandom, self‐matching manner that provides offspring with an allelic repertoire size closer to the population mean, as compared to offspring sired by the social male. This is consistent with a compatible genes model for extra‐pair mate choice where the optimal allelic diversity is intermediate, not maximal. This golden mean presumably reflects a trade‐off between maximizing pathogen recognition benefits and minimizing autoimmunity costs. Our study exemplifies how mate choice can reduce the population variance in individual MHC diversity and exert strong stabilizing selection on the trait. It also supports the hypothesis that extra‐pair mating is adaptive through altered genetic constitution in offspring.
ISSN:0962-1083
1365-294X
DOI:10.1111/mec.15273