Meeting Abstract
Socially monogamous females that engage in extra-pair copulations face potential fitness trade-offs including, but not limited to, good genes and increased genetic diversity in offspring, but also loss of paternal care and increased harassment by their social partner. Sexually transmitted pathogenic microbes have been suggested to be a cost of extra-pair copulations for female birds for nearly five decades, but this hypothesis has not yet been adequately tested. To determine how extra-pair copulations are related to the composition of the cloacal microbiome, we performed an observational study of free-living female tree swallows (Tachycineta bicolor) during the breeding season in southwestern Virginia. Tree swallows are a socially monogamous box-nesting species that exhibit high rates of extra-pair activity that vary both within and between populations. First, we characterized the cloacal microbiome of females by collecting cloacal swabs and determining the taxonomic composition of cloacal bacteria using 16s rRNA gene amplicon sequencing. Then, we used nestling paternity as a conservative proxy to estimate the frequency of extra-pair copulations and to determine the minimum number of sexual partners per female. This study increases our understanding of how sexual activity, specifically extra-pair copulations, influences the cloacal microbial communities of wild birds. Additionally, this study broadens our understanding of the potential costs of common life-history tradeoffs faced by free-living animals.
