Data from: Reproducing in hot water: experimental heatwaves deteriorate multiple reproductive traits in a freshwater ectotherm

Heatwaves are occurring at an increasing frequency and intensity under
ongoing climate change. With many reproductive traits – including mating
behaviour and gamete traits– being sensitive even to small stressors,
including short temperature changes, the impact of heatwaves on
reproduction and sexual selection processes is likely to be vast. Also,
understanding whether the sexes may differentially respond to these
extreme events is crucial to understand the impact on fecundity and the
consequence at the population level. Nonetheless, our knowledge of the
effects of heatwaves on these key aspects of an animal life is still
limited. Here, we expose recently mated male and female guppies (Poecilia
reticulata) to an experimental heatwave (32°C, 6°C above the control, for
5 days) to determine its effects on several traits, including sexual
behaviour, condition, ornamentation, and fertility. Using this design, in
contrast to most other experimental set ups, we had the possibility to
attribute the effects of the heatwave to males’ and females’ reproductive
traits independently. Overall, our results indicate that heatwaves can
drastically affect key reproductive traits and unravel sex-specific
responses. In males, there was no effect of the heatwave on survival, but
both pre- and post-copulatory reproductive traits were affected. After the
heatwave, we detected a decrease in orange colouration (the most important
ornament on which female choice is based) and the overall level of sexual
activity, and a shift in the preferred mating tactic towards forced
copulation attempts. The latter suggest implications in sexual conflict
dynamics, as forced copulations override female mate choice. Also, after
the heatwave, males had more sperm but of lower quality, and, in addition,
an increased variance in sperm number. Overall, heatwaves may result in a
compromised ability to secure mating and fertilization. In females, the
heatwave significantly affected survival, with increased mortality in the
short term, and impaired fecundity, with many females from the heatwave
treatment not reproducing at all. The negative effects of heatwaves on key
reproductive traits unravelled by our study could have major implications
for population dynamics and persistence. It highlights the need for
further studies on these extreme events on reproduction, to improve our
understanding of the impacts of climate change.