Abstract
Climate change is affecting biodiversity, but proximate drivers remain poorly understood. Here, we examine how experimental heatwaves impact on reproduction in an insect system. Male sensitivity to heat is recognised in endotherms, but ectotherms have received limited attention, despite comprising most of biodiversity and being more influenced by temperature variation. Using a flour beetle model system, we find that heatwave conditions (5 to 7 °C above optimum for 5 days) damaged male, but not female, reproduction. Heatwaves reduce male fertility and sperm competitiveness, and successive heatwaves almost sterilise males. Heatwaves reduce sperm production, viability, and migration through the female. Inseminated sperm in female storage are also damaged by heatwaves. Finally, we discover transgenerational impacts, with reduced reproductive potential and lifespan of offspring when fathered by males, or sperm, that had experienced heatwaves. This male reproductive damage under heatwave conditions provides one potential driver behind biodiversity declines and contractions through global warming.
Highlights
Climate change is affecting biodiversity, but proximate drivers remain poorly understood
We found that heatwave conditions (5 to 7 °C above the system’s optimum[29] for 5 days) damaged male reproductive potential, whereas females were largely unaffected
Female reproductive output was unaffected by the same heatwave conditions (Fig. 1)
Summary
Climate change is affecting biodiversity, but proximate drivers remain poorly understood. Impacts on individual spermatozoa were measured by exposing sperm stored within the reproductive tract of mated females to heatwave conditions, comparing against females which received the same heatwave treatment but immediately prior to mating and sperm storage (Supplementary Figure 4b).
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