Thermal phenotypic plasticity of pre- and post-copulatory male harm buffers sexual conflict in wild Drosophila melanogaster

Strong sexual selection frequently leads to sexual conflict and ensuing male harm, whereby males increase their reproductive success at the expense of harming females. Male harm is a widespread evolutionary phenomenon with a strong bearing on population viability. Thus, understanding how it unfolds in the wild is a current priority. Here, we sampled a wild Drosophila melanogaster population and studied male harm across the normal range of temperatures under which it reproduces optimally in nature by comparing female lifetime reproductive success and underlying male harm mechanisms under monogamy (i.e., low male competition/harm) vs. polyandry (i.e., high male competition/harm). While females had equal lifetime reproductive success across temperatures under monogamy, polyandry resulted in a maximum decrease of female fitness at 24°C (35%), reducing its impact at both 20°C (22%), and 28°C (10%). Furthermore, female fitness components and pre- (i.e., harassment) and post-copulatory (i.e.,..., Fitness assays: quantifying male harm
To study whether male harm is affected by temperature, we established a factorial design to measure survival and lifetime reproduction success (LRS) of female flies under monogamy (i.e., one male and one female per vial) vs. polyandry (i.e., three males and one female per vial), across three stable temperature treatments typical of this population during their reproductively active period in the wild: 20, 24, and 28°C. Comparison of female fitness at monogamy vs. polyandry is a common way to gauge male harm in Drosophila and other organisms (Yun, Agrawal, & Rundle, 2021), and our treatments reflect the low and high-end of the spectrum of sex ratios that are typical of D. melanogaster at mating patches in the wild (Dukas, 2020).
We first randomly divided virgin flies into three groups that we allocated to the three different stable temperature treatments 48 hours before starting the experiment. Flies remained at those temperatures until the end ..., Data files included are .xlsx.
We performed all statistical analyses using R statistical software.