Abstract
Genetic diversity at immune genes and levels of parasitism are known to affect patterns of (dis)assortative mating in several species. Heterozygote advantage and/or good genes should shape mate choice originating from pathogen/parasite-driven selection at immune genes. However, the stability of these associations, and whether they vary with environmental conditions, are still rarely documented. In this study, we describe mating patterns in a wild population of tree swallows (Tachycineta bicolor) over 4 years and assess the effects of haemosporidian parasite infection and immune genetic diversity at β-defensin genes on those patterns within two habitats of contrasting environmental quality, in southern Québec, Canada. We first show that mating patterns were only very weakly related to individual status of infection by haemosporidian parasites. However, we found a difference between habitats in mating patterns related to infection status, which was likely due to a non-random distribution of individuals, as non-infected mating pairs were more frequent in lower quality habitats. Mating patterns also differed depending on β-defensin heterozygosity at AvBD2, but only for genetic partners outside of the social couple, with heterozygous individuals pairing together. Our study underlines the importance of considering habitat heterogeneity in studies of sexual selection.
Highlights
Understanding the factors influencing how individuals select their reproductive partners is central in studies of sexual selection and in evolutionary ecology (Andersson, 1994; Jennions & Petrie, 1997)
We describe mating patterns in a wild population of tree swallows over 4 years, in southern Québec, Canada
Females that were not infected by haemosporidian parasites showed mating patterns in accord with random expectations
Summary
Understanding the factors influencing how individuals select their reproductive partners is central in studies of sexual selection and in evolutionary ecology (Andersson, 1994; Jennions & Petrie, 1997). This undertaking is challenging as several factors can affect mating patterns in wild populations. Genetic diversity at immune genes and parasitism are both known to affect patterns of (dis)assortative mating in several species (Hamilton & Zuk, 1982; Ejsmond, Radwan & Wilson, 2014). Effects of blood parasite infection and innate immune genetic diversity on mating patterns in a passerine bird breeding in contrasted habitats.
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