Divergent life history strategies in congeneric hyperparasitoids

Abstract

International audienceLife histories can reveal important information on the performance of individuals within their environment and how that affects evolutionary change. Major trait changes, such as trait decay or loss, may lead to pronounced differences in life history strategies when tight correlations between traits exist. Here, we show that three congeneric hyperparasitoids (Gelis agilis, Gelis acarorum and Gelis areator) that have diverged in wing development and reproductive mode employ markedly different life history strategies. Potential fecundity of Gelis sp. varied, with the wingless G. acarorum maturing a much higher number of eggs throughout life compared with the other two species. Realized lifetime fecundity, in terms of total offspring number was, however, highest for the winged G. areator. The parthenogenic G. agilis invests its resources solely in females, whilst the sexually reproducing species both invested heavily in males to reduce competitive pressures for their female offspring. Longevity also differed between species, as did the direction of the reproduction-longevity trade-off, where reproduction is heavily traded off against longevity only in the asexual G. agilis. Resting metabolic rates also differed between the winged and wingless species, with the highest metabolic rate observed in the winged G. areator. Overall, these geline hyperparasitoids showed considerable divergence in life history strategies, both in terms of timing and investment patterns. Major trait changes observed between closely related species, such as the loss of wings and sexual reproduction, may contribute to the divergence in key life history trait

Spatial and temporal diversity in hyperparasitoid communities of Cotesia glomerata on garlic mustard, Alliaria petiolata

“…Specialists are evolutionarily required to 'track' their hosts and are therefore under much stronger selection than generalists to locate cocoons of C. glomerata occurring in different habitats. Wingless hyperparasitoids may have evolved to broaden their host range while trading off traits like wings for reduced fecundity and increased longevity (Harvey, 2008;Harvey et al, 2017;Visser et al, 2014Visser et al, , 2016. By contrast, the Gelis species are considered to be extreme generalists that will attack hosts as phylogenetically divergent as spider egg sacs, moth pupae and parasitoid cocoons (Bezant, 1956;Russell, 1987;Cobb & Cobb, 2004).…”

“…Previous studies have shown that some species of the Gelis genus have life spans of 70 days without hosts at ambient temperatures (Harvey, 2008;Harvey et al, 2015Harvey et al, , 2017Visser et al, 2016). Around this time, it is rare to see a cabbage white butterfly adult, let alone their larvae.…”

“…Search area covered per unit of time is clearly limited in wingless species, compared with winged species that can cover larger distances, and stronger specialisation would not be very beneficial. Wingless hyperparasitoids may have evolved to broaden their host range while trading off traits like wings for reduced fecundity and increased longevity (Harvey, 2008;Harvey et al, 2017;Visser et al, 2014Visser et al, , 2016.…”

“…This raises the question as to where these early hyperparasitoids come from and why they are already active during times when their hosts are not yet present. Previous studies have shown that some species of the Gelis genus have life spans of 70 days without hosts at ambient temperatures (Harvey, 2008;Harvey et al, 2015Harvey et al, , 2017Visser et al, 2016). As metabolic rates generally decrease with falling temperatures, it is expected that life span could be even higher under colder temperature regimes, so it could be that these species overwinter during the adult stage and oviposit at the first opportunity that is presented.…”

Reproduction and Offspring Sex Ratios Differ Markedly among Closely Related Hyperparasitoids Living in the Same Microhabitats

“…For example, when plenty of resources are available, mating patterns in parasitoid populations generally select for equal parental investment into both sexes. However, when vital resources, such as mates or hosts, are scarce or limiting, increased competition can generate conditions that bias sex ratios in the direction of either sex (King 1987;Visser et al, 2016).…”