Female house sparrows "count on" male genes: experimental evidence for MHC-dependent mate preference in birds

Matteo Griggio,Dustin J Penn,Clotilde Biard,Herbert Hoi

doi:10.1186/1471-2148-11-44

Abstract

BackgroundFemales can potentially assess the quality of potential mates using their secondary sexual traits, and obtain "good genes" that increase offspring fitness. Another potential indirect benefit from mating preferences is genetic compatibility, which does not require extravagant or viability indicator traits. Several studies with mammals and fish indicate that the genes of the major histocompatibility complex (MHC) influence olfactory cues and mating preferences, and such preferences confer genetic benefits to offspring. We investigated whether individual MHC diversity (class I) influences mating preferences in house sparrows (Passer domesticus).ResultsOverall, we found no evidence that females preferred males with high individual MHC diversity. Yet, when we considered individual MHC allelic diversity of the females, we found that females with a low number of alleles were most attracted to males carrying a high number of MHC alleles, which might reflect a mating-up preference by allele counting.ConclusionsThis is the first experimental evidence for MHC-dependent mating preferences in an avian species to our knowledge. Our findings raise questions about the underlying mechanisms through which birds discriminate individual MHC diversity among conspecifics, and they suggest a novel mechanism through which mating preferences might promote the evolution of MHC polymorphisms and generate positive selection for duplicated MHC loci.

Highlights

Females can potentially assess the quality of potential mates using their secondary sexual traits, and obtain “good genes” that increase offspring fitness
We did not detect an overall preference for males with either low, medium or high major histocompatibility complex (MHC) diversity, but when we considered the individual MHC allelic diversity of the females, we found that low diversity females spent significantly more time in front of the high diversity male (i.e. HM; GLMM analysis for 54 trials: female group: F 2,130 = 0.45, P = 0.64; stimulus group: F 2,130 = 2.11, P = 0.13; female group*stimulus group: F 4,130 = 3.82, P = 0.006; Figure 2, see Table 1 and Table 2)
It is unclear whether our findings predict actual mating patterns in the wild, they are consistent with an observational study on a wild population of house sparrows that found evidence that females avoid mating with males with low individual MHC diversity [28]

Summary

Introduction

Females can potentially assess the quality of potential mates using their secondary sexual traits, and obtain “good genes” that increase offspring fitness. Jerram Brown decided to “put aside the idea that there is a best male and that he is best for every female,” and instead, he argued that females should prefer genetically compatible or heterozygous males to increase offspring heterozygosity or genetic diversity [2] ( see [3,4,5]). He was inspired by studies on house mice (Mus musculus) that found disassortative mating preferences for genes of the major histocompatibility complex (MHC) [6,7]. Observational studies in the wild and experimental studies on cryptic mate preferences provide intriguing evidence that MHC genes influence mating preferences in birds

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