Small-scale spatial resource partitioning in a hyperparasitoid community

Abstract

International audiencePlant-herbivore-natural enemy associations underpin ecological communities, and such interactions may go up to four (or even more) trophic levels. Here, over the course of a growing season, we compared the diversity of secondary hyperparasitoids associated with a common host, Cotesia glomerata, a specialized larval endoparasi-toid of cabbage butterfly caterpillars that in turn feed on brassicaceous plants. Cocoon clusters of C. glomerata were pinned to ~30 Brassica nigra plants by pinning them either to branches in the canopy (~1.5 m high) or to the base of the stem near the ground. The cocoons were collected a week later and reared to determine which hyper-parasitoid species emerged from them. This was done in four consecutive months (June–September). Cocoons placed in the canopy were primarily attacked by specialized winged hyperparasitoids (Lysibia nana, Acrolyta nens), whereas cocoons on the ground were attacked by both winged and generalist wingless hyperparasitoids (Gelis acarorum, G. agilis), although this changed with season. There was much more temporal variation in the diversity and number of species attacking cocoons in the canopy than on the ground; the abundance of L. nana and A. nens varied from month to month, whereas P. semotus was only prevalent in August. By contrast, G. acarorum was abundant in all of the samples placed near the ground. Our results show that hyperparasitoids partition host resources at remarkably small vertical spatial scales. We argue that spatial differences in the distribution of natural enemies can contribute to the diversity patterns observed in the field

Honeydew composition and its effect on life‐history parameters of hyperparasitoids

“…By contrast, G. agilis is wingless and can cover a smaller area per unit of time compared with A. nens. Wingless Gelis species appear to prefer searching for hosts on or close to the ground instead of in the canopy of forbs (Harvey et al, 2014;Heinen & Harvey, 2019). Honeydew excreted by aphids not only accumulates on leaf surfaces of the food plant, but also falls to the ground (Moller & Tilley, 1989).…”

Spatial distribution and niche partitioning in the Ooencyrtus spp. complex parasitizing the eggs of Stenozygum coloratum

“…Niche partitioning often occurs on a temporal or spatial basis (Albrecht and Gotelli 2001;Harvey et al 2014;Moya-Raygoza et al 2012;Trizzino et al 2014;van Baaren et al 2004). Partitioning may occur on a relatively small scale, e.g., the height of a tree (Harvey et al 2014), or on a much larger scale such as elevation range (MoyaRaygoza et al 2012;Trizzino et al 2014). In parasitoids, coexistence may also be maintained by interspecific differences in various biological features related to host (common resource) exploitation, which might give each species an advantage over the others under specific conditions.…”

Simulated heatwave conditions associated with global warming affect development and competition between hyperparasitoids

“…Several field studies have found that L. nana and A. nens frequently emerge from single cocoon clusters of C. glomerata in the field, strongly suggesting that they do compete for hosts (Poelman et al 2013, Harvey et al 2014, Zhu et al 2015. Furthermore, cocoons of C. glomerata remain suitable for parasitism for less than four days at 25°C (Harvey et al 2006), and this decreases rapidly under warmer conditions .…”

“…Both species are idiobionts that attack non-growing host stages or prevent further host development and are largely specialized on cocoons of Cotesia species in nature, with C. glomerata appearing to be one of their more important hosts (Shwarz and Shaw 2000). The two hyperparasitoids appear to be bi-voltine and have very overlapping niches, both spatially and temporally (Harvey et al 2014). Several field studies have found that both species frequently emerge from single cocoon clusters of C. glomerata in the field, strongly suggesting that they do compete for hosts (Poelman et al 2013, Harvey et al 2014, Zhu et al 2015.…”

“…The two hyperparasitoids appear to be bi-voltine and have very overlapping niches, both spatially and temporally (Harvey et al 2014). Several field studies have found that both species frequently emerge from single cocoon clusters of C. glomerata in the field, strongly suggesting that they do compete for hosts (Poelman et al 2013, Harvey et al 2014, Zhu et al 2015. To address whether different temperature regimes affect the outcome of larval competition in the two species, we simulated three day-night temperature regimes in climate cabinets representing cool, normal and hot summer conditions in the Netherlands where the two species are native.…”