Divergence in sex peptide-mediated female post-mating responses in Drosophila melanogaster.

Kristina U Wensing,Claudia Fricke

doi:10.1098/rspb.2018.1563

Kristina U Wensing, Claudia Fricke

Open Access

https://doi.org/10.1098/rspb.2018.1563

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Abstract

Transfer and receipt of seminal fluid proteins crucially affect reproductive processes in animals. Evolution in these male ejaculatory proteins is explained with post-mating sexual selection, but we lack a good understanding of the evolution of female post-mating responses (PMRs) to these proteins. Some of these proteins are expected to mediate sexually antagonistic coevolution generating the expectation that females evolve resistance. One candidate in Drosophila melanogaster is the sex peptide (SP) which confers cost of mating in females. In this paper, we compared female SP-induced PMRs across three D. melanogaster wild-type populations after mating with SP-lacking versus control males including fitness measures. Surprisingly, we did not find any evidence for SP-mediated fitness costs in any of the populations. However, female lifetime reproductive success and lifespan were differently affected by SP receipt indicating that female PMRs diverged among populations. Injection of synthetic SP into virgin females further supported these findings and suggests that females from different populations require different amounts of SP to effectively initiate PMRs. Molecular analyses of the SP receptor suggest that genetic differences might explain the observed phenotypical divergence. We discuss the evolutionary processes that might have caused this divergence in female PMRs.

Highlights

Mating induces dramatic changes in female behaviour, physiology and gene expression that together constitute female post-mating responses (PMRs)
We investigated whether female PMRs to a specific sexually antagonistic signal, ejaculatory sex peptide (SP), diverged across three wild-type D. melanogaster populations, and whether we can detect signs of sexually antagonistic coevolution between SP and female PMRs
We present means + s.e. calculated from raw pdaffiffitffiaffiffiffi.ffiffiFffiffiffioffiffiffirffiffiffipffiffiffirffiffioportion data, we calculated the standard error as p(1 À p)=n, where p is the proportion across all replicates and n is the sample size

Summary

Introduction

Mating induces dramatic changes in female behaviour, physiology and gene expression that together constitute female post-mating responses (PMRs). Male seminal fluid proteins (SFPs) are found in many taxa [2,3] and have been well studied in Drosophila melanogaster where specific functions for several of the more than 130 SFPs have been identified and are responsible for invoking the majority of the female PMRs [4] These SFPs are known to evolve rapidly [5,6] and coevolve with targets inside the female [7]. Single nucleotide polymorphisms in the SP and SPR genes and their interaction affect sperm competition success and female remating [26] This makes them promising candidates to study sexually antagonistic coevolution at the phenotypic and molecular level.

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