The effects of extreme heat on the reproduction in a worldwide-invasive and synanthropic spider Steatoda grossa.

Reproduction is vital for the persistence of a species. Reproductive success is influenced by biotic and abiotic factors. In sexually reproducing organisms, mating strategy and behaviour are important biotic factors affecting reproduction by optimizing fitness. Spiders are ectotherms and their body temperature and physiology are largely determined by ambient temperature. Temperature extremes due to anthropogenic climate change are predicted to increase in severity, duration and frequency. Extreme temperature events exert levels of stress to reproduction, in particular, because the upper thermal threshold for reproduction is often lower than for survival of a species. Moreover, the negative effects of exposure to extreme heat are predicted to be stronger for higher trophic level ectotherms, such as spiders. Spiders have fascinating sexual selection strategies, however how these strategies and exposure to heat influence fertility is largely unknown. I will first study mating strategy and behaviour in the synanthropic spider, Steotoda grossa, under conditions of male-male competition to reveal the details of courtship behaviour, mating success, and then using and simulated mating disturbance to understand how this affects female reproductive success. Second, I will investigate how exposure to heat of adults at mating will affect reproduction. In an additional experiment I will study the effect of heat exposure on egg sac development. As the most abundant natural predator of insects, spiders are integral to the biological control of pests. This study will help to understand the reproduction success of a sedentary, web-building spider species under mating disruption and heat stress.