Host-Size Mediated Trade-Off in a Parasitoid Sclerodermus harmandi

Abstract

Optimality models of host-parasitoid relationships have traditionally assumed that host quality increases as a function of host size at parasitism. However, trade-offs may play a crucial role in species evolution and should be found in host-parasitoid interactions where the host quality may differ between different sizes. Here, we investigated the effects of host size differences of Monochamus alternatus larva on foraging decisions, parasitism and related fitness in a gregarious ectoparasitoid, Sclerodermus harmandi. Two-choice and non-choice experiments were conducted with M. alternatus larvae to evaluate preference and performance of S. harmandi, respectively. Results from two-choice test showed that adult females prefer to attack large larvae rather than small larvae. In no-choice tests, adult females needed more time to paralyze large larvae than small larvae before laying eggs on the body surface of M. alternatus larvae and had lower survival and parasitism rate on those large larvae. Foraging decisions of S. harmandi led to the selection of the most profitable host size for parasitoid development, which showed more offspring gained on large M. alternatus larvae than on small larvae and got higher body weight on those large hosts. This study demonstrates the existence of trade-off occurring during host-parasitoids interactions according to host size related quality.

Reproductive biology of Sclerodermus brevicornis, a European parasitoid developing on three species of invasive longhorn beetles

“…This resulted in browning of the epidermis and sometimes in visible lacunae. Host feeding appeared to promote the longevity of the adult parasitoids and is likely to enhance future fecundity as Sclerodermus are synovigenic anautogenous species (oogenensis takes place after foundress feed on a suitable host) (Liu et al, 2011). In conclusion, this behavior may have some pest control value as S. brevicornis attacks and kills small hosts, even if it does not generate recruits into the next generation of parasitoids.…”

“…In other species in the same genus it was further shown that the occurrence of all-male broods at emergence was related to high developmental mortality and to broods produced by few unmated foundresses (Kapranas et al, 2016b). On the basis of evidence from other Sclerodermus species (Mamaev, 1979;Liu et al, 2011;Tang et al, 2014;Kapranas et al, 2016b), it is likely that S. brevicornis foundresses each lay a small number of male eggs in every clutch and the proportion of all-female broods reflects the probability of those eggs failing to develop to adulthood. We noted that there were no all-female broods produced on ALB hosts and that this host species also yielded the largest S. brevicornis broods, suggesting a low preimaginal mortality.…”

“…We have shown that S. brevicornis can attack and develop on three invasive longhorn beetle species becoming a strong candidate for biological control programs based on mass-rearing and release protocols. We, however, note that our study, like some studies on congenerics (Liu et al, 2011), has been restricted to evaluating parasitoid performance when hosts are exposed directly to foundresses. It would be informative to evaluate S. brevicornis performance under more natural conditions given that females must forage for hosts within wood and may encounter a variety of host species at different development stages, in competition with other foundresses.…”

“…After laying eggs, mothers remain at the host, tending the offspring until pupation into cocoons and emergence of adults (Hu et al, 2012;Yang et al, 2012;Tang et al, 2014). Multiple-female reproduction on a single host appears to be cooperative, without division of labor, and as such may be termed quasi-social Liu et al, 2011;Wang et al, 2016), an unusual life-history character among parasitoid hymenopterans.…”

Tendency and consequences of superparasitism for the parasitoid Ooencyrtus pityocampae (Hymenoptera: Encyrtidae) in parasitizing a new laboratory host, Philosamia ricini (Lepidoptera: Saturniidae)

“…However, the outcome depends on host quality, which for parasitoids is associated with the following features of the host: species, shape, size, movement, sound, chemical cues (Vinson, 1976) and age (Colinet et al, 2005). Generally large and young insects are the best hosts for wasps (Da Rocha et al, 2006;Liu et al, 2011). Parasitoids prefer hosts that are the best sources of nutrients for their offspring, and hymenopteran wasps adjust their sex ratios according to host quality in a way that maximizes the benefi ts.…”