Parasitoid-host associations in invaded communities

Authors: Duan, Jian; QUINN, NICOLE - University Of Florida; Weber, Donald

Submitted to: Current Opinion in Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/8/2024
Publication Date: 8/12/2024
Citation: Duan, J.J., Quinn, N.F., Weber, D.C. 2024. Parasitoid-host associations in invaded communities. Current Opinion in Insect Science. 65. https://doi.org/10.1016/j.cois.2024.101250.
DOI: https://doi.org/10.1016/j.cois.2024.101250

Interpretive Summary: Parasitic insects (or parasitoids) are important members of nearly all land-based ecosystems and many are beneficial natural enemies of agriculture and forest insect pests. In nature, many parasitoids attack more than one species of hosts, and the majority of hosts are attacked by several species of parasitoids. This opens many potential opportunities for ecological interactions of invasive species with native parasitoid and host association networks in invaded communities. Here we reviewed and analyzed data from published literature on parasitoid-host associations under one major aspect of global change – biological invasion, which is a leading cause of biodiversity loss. We conclude that the complexity of interactions between invasive species and local parasitoid-host association networks, and its ecological consequences, may vary with the trophic level of intrusion, invasive species, as well as the attributes of invaded communities. Biological control of insect pests via specific parasitoid host associations in agricultural, forests and/or natural ecosystems should consider such complexity and implications. Our review should be of interest to scientists and managers interested in the impacts of invasive species on ecosystems, ecosystem services, and natural resources.

Technical Abstract: Parasitoids are important members of nearly all terrestrial ecosystems. In nature, most parasitoids attack more than one species of hosts, and the majority of hosts are attacked by several species of parasitoids. This opens many potential opportunities for ecological interactions of invasive species with native parasitoid and host association networks in invaded communities. The complexity of interactions between invasive species and local parasitoid-host association networks, and its ecological consequences, may vary with the trophic level of intrusion, invasive species, as well as the attributes of invaded communities. Invasive plants have been documented as a major cause of ecosystem degradation worldwide through bottom-up trophic and associational interactions with native insect communities. However, invasive plant species in some communities may variously result in negative, positive, and non-significant impacts to insect communities including herbivorous insects and associated native parasitoids, depending on the plant species, insect taxon, functional group, and ecosystems. In contrast, invasive herbivorous insects can serve as novel or alternative hosts to native parasitoids (and predators), leading to formation of new associations with native generalist parasitoids, which may in turn result in enhanced suppression of the invasive insects or significant reduction of native hosts and associated natural enemies. Invasive herbivorous insects can be antagonistic competitors to native phytophagous insects, cascading the antagonistic effects via trophic web to the associated parasitoid community, leading to reduction of the abundance of specialist parasitoids and/or host range expansion or shift of generalist parasitoids. Invasive insect pests have the potential to functionally exterminate host plant species in entire regions or habitats, thus profoundly affecting native plant-based insect communities, including herbivores and their natural enemies (parasitoids). Likewise, invasive plant pathogens can transform ecosystems by causing functional extinction of dominant species such as the American chestnut. Parasitoids have been among the most important groups of insect natural enemies commonly used for classical biological control of agriculture and forest insect pests. Perhaps because of this reason, literatures rarely use the term “invasive parasitoids” to describe both purposely introduced and adventive (unintentionally introduced) as “invasive species”. However, adventive parasitoids can become significant invasive species in the expanded geographic range, exerting significant top-down effects on local insect herbivorous insect communities, even leading to exclusion of associated native parasitoid communities. Like primary parasitoids providing top-down control of their hosts, hyperparasitoids can exert top-down control of primary parasitoids. Without the top-down pressure provided by hyperparasitoids, parasitoids might reproduce relatively unchecked, thereby increasing host mortality, which could have cascading impacts on trophic interactions throughout the ecosystem. In addition, invasive hyperparasitoids could outcompete and displace native hyperparasitoids, although this remains undocumented. We conclude that parasitoid-host association networks in invaded communities are complex, dynamic and subject to trophic intrusions from invasive plants, herbivores, parasitoids and hyperparasitoids. Future studies should take a holistic systems approach to understanding the impact of biological invasion and its consequences in shaping community structure through altering existing native, coevolved parasitoid-host association networks.