Sex-specific sterility caused by extreme temperatures is likely to create cryptic changes to the operational sex ratio in Drosophila virilis

Climate change is increasing the frequency and severity of short-term heat
shocks that threaten the persistence of natural populations. The effect of
thermal stress on natural selection is a common topic of debate, but high
temperatures can also influence sexual selection. Typically, males and
females of a species can survive at similar extreme temperatures, but
males have been shown to lose fertility at lower temperatures than
females. Here, we examine how a brief exposure of pupae to high
temperatures in the fruit fly Drosophila virilis affects adult fertility
in both males and females. We find strong sexual dimorphism in
temperature-induced sterility. This has the potential to quickly and
unpredictably create populations composed of mostly sterile males and
fertile females, resulting in changes to the operational sex ratio (OSR).
These disruptions are likely to be cryptic and difficult to measure in the
wild, especially considering that males can eventually recover fertility
and that sterile males of some species can still copulate. Changes to the
OSR in this way are likely to influence sexual selection by favouring
females that can discriminate between fertile and sterilised males, and
possibly leading to female-female conflict over a limited pool of fertile
males. Further research on how cryptic disruptions to the OSR affect
sexual selection dynamics is critical for understanding the impact of
environmental change on biodiversity.