Climate change can impact ecological communities in many ways, including altering the niche breadth of component species. But precisely how abiotic change such as warming interacts with biotic factors to determine niche breadth remains unclear. Host-parasitoid systems offer a unique opportunity to investigate this important question. Many studies have documented how climate affects host-parasitoid interactions, and there are also the possibilities with this system to perform experimental works. Drosophila species and their parasitoids are one such group. In this study, we examine how warming impacts host-parasitoid interactions, specifically focusing on the shift of their niche breadth. We set out to address three questions 1) Does elevated temperature reduce the change in the degree of specialization for parasitoids? 2) Does the presence of multiple parasitoids narrow alter the diet breadth of parasitoids? 3) Is temperature and parasitoid niche-breadth correlated? What are the impacts on their life-history traits? We conducted laboratory experiments using a naturally co-occurring Australian Drosophila-parasitoid system at three temperatures. Here, 24°C is ambient temperature, 28°C is experimental warming, and 20°C is the coldest temperature they experience in the field. Seven host species and three larval parasitoid species were tested and reared for a total of 58,500 individuals.
Results/Conclusions
Results from question one showed that experimental warming caused a decrease in niche breadth across the three parasitoid species, and that successful hatching rate was significantly lower at 28°C. Among the three species Leptopilina sp. is a specialist, specialization follow by Asobara sp., and Ganaspis sp. is a generalist. The results from multiple parasitoid species showed that niche breadth decreased when multiple parasitoid species were present, but the niche breadth of the specialist occasionally increased when in the presence of other parasitoid species. In this experiment, we also found that temperature impacted the diet breadth of the generalist species more strongly than the specialist species. Finally, as temperature increased, mean interaction strength increased as a consequence of the narrowing of parasitoid diet breadth. Changes in temperature affect life-history traits, and significantly shifted trait values (mean and variance) in developmental time, body size and sex ratio of parasitoids. This has the potential to alter host-parasitoid community structures. Our study provides a better understanding of how climate change could impact the complex pattern of interactions in host-parasitoid communities, with implications for predicting the consequences for biological control and ecosystem functioning.