Extrinsic Inter- and Intraspecific Competition in Parasitoid Wasps

Abstract

The diverse ecology of parasitoids is shaped by extrinsic competition, i.e., exploitative or interference competition among adult females and males for hosts and mates. Adult females use an array of morphological, chemical, and behavioral mechanisms to engage in competition that may be either intra- or interspecific. Weaker competitors are often excluded or, if they persist, use alternate host habitats, host developmental stages, or host species. Competition among adult males for mates is almost exclusively intraspecific and involves visual displays, chemical signals, and even physical combat. Extrinsic competition influences community structure through its role in competitive displacement and apparent competition. Finally, anthropogenic changes such as habitat loss and fragmentation, invasive species, pollutants, and climate change result in phenological mismatches and range expansions within host–parasitoid communities with consequent changes to the strength of competitive interactions. Such changes have important ramifications not only for the success of managed agroecosystems, but also for natural ecosystem functioning. Expected final online publication date for the Annual Review of Entomology, Volume 67 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Multiple parasitoid species enhance top‐down control, but parasitoid performance is context dependent

“…Parasitoids can compete both as adults for oviposition (i.e. extrinsic competition or interference; Ode et al, 2022) and as larvae within a host (i.e. intrinsic competition; Harvey et al, 2013).…”

Multiple parasitoid species enhance top-down control, but parasitoid performance is context-dependent

“…Our case seems different because successful parasitism rates did not increase for both parties, implying competitive interaction between the parasitoids. Parasitoids can compete both as adults for oviposition (i.e., extrinsic competition or interference; Ode et al, 2022) and as larvae within a host (i.e., intrinsic competition; Harvey et al, 2013). Extrinsic competition has adverse effects on parasitoid attack rates, linked to search efficiency and handling time, leading to a potential decrease in host mortality (Xu et al, 2016).…”

Population level interactions between an invasive woodwasp, an invasive nematode and a community of native parasitoids

“…Parasites share hosts by infecting different individuals in host populations and by co-infecting the same host individuals. Thus, interactions among parasites occur indirectly due to exploitative competition for shared hosts or directly through interaction outside the host (Ode et al 2021), as well as within host individuals (van Nouhuys and Punju 2010; Harvey et al 2013). Because parasite species are each independently sensitive to host density, the strengths of their interactions with each other and with hosts can change with host density.…”