Elevated temperatures have sex-specific effects on nuptial gift behavior

Increasing developmental temperatures are well-known to impact fertility, yet their effects on pre-copulatory behaviors, despite having clear fitness consequences, are often overlooked. In many species, male nuptial gift presentation during courtship plays an important role in sex-specific mate choice, fitness, and subsequent co-evolutionary dynamics. However, developmental temperature effects on nuptial gift behaviors and their implications for population fitness remain unknown. Heat-induced changes to male behavior may signal fertility, driving female discrimination, particularly in monandrous systems where exclusively pairing with an infertile male threatens population growth. Additionally, as nuptial gift production is costly, the differential allocation hypothesis suggests males should adjust gift investment based on female fitness. Here, we investigated how elevated developmental temperature affects nuptial gift behavior, mating likelihood, and reproductive output in the monandrous species Drosophila subobscura. Individuals developed at either a control or stressful temperature, and fully factorial no-choice mating tests were used to identify sex-specific effects of heat stress. Heat-stressed males were largely infertile, less likely to mate, present a gift, or have a gift accepted, suggesting nuptial gifts may signal male fertility and influence female mate choice. Heat-stressed females were also less likely to mate, receive a gift, and were presented with fewer gifts from heat-stressed males. As heat-stressed females required more gifts to match the reproductive output of controls, selection may drive male mate choice through strategic resource allocation. These findings highlight how climate change may significantly impact sex-specific mate choice, with important implications for selection on pre-copulatory courtship traits and population dynamics.