Seeing-good-gene-based mate choice: From genes to behavioural preferences.

David Richardson,Li Sun,Qiu‐Hong Wan,Graham N Stone,Tong Zhou,Sheng‐Guo Fang

doi:10.1111/1365-2656.13071

David Richardson, Li Sun + Show 4 more

Open Access

https://doi.org/10.1111/1365-2656.13071

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Abstract

Although vertebrates have been reported to gain higher reproductive outputs by choosing mates, few studies have been conducted on threatened species. However, species recovery should benefit if natural mate choice could improve reproductive output (i.e. pair performance related to offspring number, such as increased clutch size, numbers of fertilized egg and fledglings). We assessed the evidence for major histocompatibility complex (MHC)‐based mate preference in the endangered crested ibis (Nipponia nippon) and quantified the impacts of such choice on reproductive output.We tested the hypothesis that crested ibis advertise “good genes” through external traits, by testing whether nuptial plumage characteristics and body morphology mediate mate choice for underlying genetic MHC variation.We found differences between males and females in preferred MHC genotypes, external traits used in mate choice and contributions to reproductive outputs. Females preferred MHC‐heterozygous males, which had darker [i.e. lower total reflectance and ultraviolet (UV) reflectance] nuptial plumage. Males preferred females lacking the DAB*d allele at the MHC class II DAB locus, which had higher average body mass. DAB*d‐free females yielded heavier eggs and more fledglings, while MHC‐heterozygous males contributed to more fertilized eggs and fledglings. Fledging rate was highest when both parents had the preferred MHC genotypes (i.e. MHC‐heterozygous father and DAB*d‐free mother). Comparisons showed that free‐mating wild and semi‐natural pairs yielded more fertilized eggs and more fledglings, with a higher fledging rate, than captive pairs matched artificially based on pedigree.Conservation programmes seldom apply modern research results to population management, which could hinder recovery of threatened species. Our results show that mate choice can play an important role in improving reproductive output, with an example in which an endangered bird selects mates using UV visual capability. Despite the undoubted importance of pedigree‐based matching of mates in conservation programmes, we show that free mating can be a better alternative strategy.

Highlights

To test whether mate choice may be based on genome‐wide genetic diversity, we examined relationships between reproductive success and genome‐ wide genetic diversity estimated with a panel of microsatellites
We found that male major histocompatibility complex (MHC) heterozygosity was negatively correlated with nuptial plumage colorant reflectance (Figure 2) but not with body morphology (Table S6, Figure S4), while female DAB*d presence was negatively correlated with body morphology (Figure 3c, d) but not with colorant reflectance (Table S7)
Our results show that crested ibises exhibit mutual MHC‐based mate preferences that may rely on external visual cues, and that

Summary

Introduction

3. We found differences between males and females in preferred MHC genotypes, external traits used in mate choice and contributions to reproductive outputs. We asked whether external traits (i.e. nuptial plumage characteristics, body size and body mass) could be used as cues by male and/or female crested ibis for selection of mates with specific MHC genotypes, leading to enhanced reproductive outputs.

Results

Conclusion