Negative effect of global warming on biological control is mitigated by direct competition between sympatric parasitoids

Abstract

Parasitoids are among the most important and successful groups of natural enemies used in the biological control of insect pests. In most systems, several parasitoid species can parasitize the same pest. The coexistence of parasitoids in agroecosystems and their efficacy as biological control agents may be disrupted by global warming. An increase of approximately 3°C is predicted by the end of the twenty-first century in the Mediterranean basin (IPCC, 2014). In this context, we compared the present and future performance of two sympatric parasitoids of the genus Aphytis (Hymenoptera: Aphelinidae), which control the armoured scale Aonidiella aurantii (Hemiptera: Diaspididae) in Mediterranean citrus, either alone or in combination. The net reproductive rate (R0) of the introduced Aphytis melinus DeBach was higher than that of its competitor, the native Aphytis chrysomphali (Mercet), under current conditions. The two parasitoids responded differently to higher temperature and competition. The R0 of A. chrysomphali decreased by 50% when both parasitoids competed in the same patch, but was not affected by the temperature increase. The R0 of A. melinus decreased approximately 40% with the increase in temperature because the proportion of females was reduced. However, the presence of A. chrysomphali competing in the same patch mitigated the negative effect of the increase in temperature on A. melinus (R0 decreased by only 20%). Overall, our results suggest that global warming will have a negative effect on the biological control of A. aurantii and that this effect will be higher in areas, such as southern Spain, where A. melinus has displaced A. chrysomphali.

A global parasite conservation plan

“…These isolated data points are far more sparse than predicted by coextinction theory, a "paradox of missing coextinctions" (Strona et al, 2013). Recent research has begun to explore how climate change and other anthropogenic drivers might directly threaten parasites, separate from host vulnerability (Carlson et al, 2017a), but these projections are also unvalidated; despite important evidence from isolated studies (Bush et al, 2013;Cebolla et al, 2018;Esser et al, 2019;Zhan et al, 2018), no systematic effort has been undertaken to document parasite range loss or prevalence declines. The few long-term datasets that exist are biased towards parasites of zoonotic or economic concern that are increasing (or projected to increase) in abundance or geographic range (Cizauskas et al, 2017;Fiorenza et al, n.d.;Howard et al, 2019).…”

Presence of multiple parasitoids decreases host survival under warming, but parasitoid performance also decreases

“…In addition to an increase in prey suppression with multiple predators under warming in terrestrial ecosystems, a diverse predator community also increases the chances of complementarity in face of environmental variation and disturbance (Macfadyen, Craze, Polaszek, van Achterberg, & Memmott, 2011). Indeed, presence of multiple predator species could mitigate negative effects of warming on top-down control due to resource partitioning and/or functional redundancy (Cebolla, Urbaneja, Baaren, & Tena, 2018;Drieu & Rusch, 2017;Pepi & McMunn, 2021). Preserving predator biodiversity should therefore be generally beneficial for topdown control under climate change.…”

“…In addition to increasing prey suppression with multiple predators under warming in terrestrial ecosystems, a diverse predator community also increases the chances of complementarity in the face of environmental variation and disturbance [48]. Indeed, the presence of multiple predator species could mitigate the adverse effects of warming on top-down control due to resource partitioning and/or functional redundancy [47,49,50].…”

Effects of elevated CO2 and temperature on survival and wing dimorphism of two species of rice planthoppers (Hemiptera: Delphacidae) under interaction

“…Interspecific interaction among phytophagous insects sharing the same food plant is widespread when resources are limiting . The effect of climate change on interspecific interaction can be direct, via affecting their physiology, behavior, and phenology, or indirect, through climate‐induced changes in the quality of their food resources . The responses of insects in interspecific interaction to anthropogenic climate change (ACC) are likely to be both complex and variable, which may largely depend on life histories and traits of the insects …”