The evolution of parasitoid fecundity: a paradigm under scrutiny

Abstract

An important assumption in insect parasitoid life-history theory is that, within parasitoid complexes (species assemblages associated with particular hosts), members attacking young host stages are more fecund than members targeting older ones. This hypothesis reflects the general trajectory of host survivorship curves: as a host cohort ages, availability to female parasitoids declines, as can the risk that the host - and the parasitoid offspring it carries - succumbs to extrinsic mortality. However, the analyses that provided empirical support for the hypothesis did not control for phylogeny. Using the original datasets, we use phylogenetically corrected analyses to test whether the results of the seminal study are upheld. Although we show those findings to be robust, the decline in fecundity could be a sampling artefact. We conclude that it would be unwise to assume the paradigm to be generally representative of natural parasitoid complexes.

Comparing parasitoid life histories

“…These traits are likely to exert important selective effects on parasitoid life histories (Price, , ; Ellers et al., ; Ellers & Jervis, , ), but are sparsely measured. Measures of host concealment and host stage attacked are sometimes used as proxies for both, though possibly not effectively (Jervis et al., ).…”

“…In general, life‐history models emphasize the importance of considering both adult and juvenile mortality, because the difference between the two exerts a strong selective force (Stearns, ): for example, increasing adult mortality relative to juvenile mortality can select for delayed maturation and hence higher fecundity in fish (Law & Grey, ) and semelparity in plants (Young, ). It is a pity that no life‐history models in parasitoids have explicitly considered the effects of independently varying externally imposed juvenile and adult mortality rates; hence, the precise selective effects of mortality risks are not well‐bedded in parasitoid‐specific theory, even though predictions have been made about empirical patterns (Jervis et al., ).…”

The link between host density and egg production in a parasitoid insect: comparison between agricultural and natural habitats

“…In seminal work, Price (, ) demonstrated that parasitoids in the family Ichneumonidae attacking younger host stages, which are more abundant in the environment, are more fecund than those targeting later host stages. Jervis, Moe & Heimpel () validated Price's results while controlling for phylogeny, although they found no support for the hypothesis in a taxonomically broader data set. Additional evidence comes from synovigenic parasitoids, where females continue producing eggs throughout their adult lives.…”

Effect of temperature on the reproductive biology ofPeristenus spretus(Hymenoptera: Braconidae), a biological control agent of the plant bugApolygus lucorum(Hemiptera: Miridae)

“…The evaluation of a biological control agent requires the collection of detailed A c c e p t e d M a n u s c r i p t information on its life history traits, including aspects of immature stage development and the female's reproductive strategy (Haye, Broadbent, Whistlecraft, & Kuhlmann, 2005;Jervis et al, 2012).…”

“…Several biological attributes affect the potential effectiveness of parasitoids, such as development rate (Bürgi & Mills, 2013), larval survival (Qiu, Zhou, Luo & Xu, 2012), adult longevity (Winkler, Wäckers, Bukovinszkine-Kiss & Van Lenteren, 2006), sex ratio (Berndt & Wratten, 2005), fecundity (Jervis, Moe & Heimpel, 2012;Wakefield, Bell & Gatehouse, 2010), host specificity (Jenner, Kuhlmann, Miall, Cappuccino & Mason, 2014;Murray, Withers & Mansfield, 2010), and functional response (Latham & Mills, 2012;Luo, Li, Lu, Zhang, Haye, Kuhlmann & Wu, 2014b). The evaluation of a biological control agent requires the collection of detailed A c c e p t e d M a n u s c r i p t information on its life history traits, including aspects of immature stage development and the female's reproductive strategy (Haye, Broadbent, Whistlecraft, & Kuhlmann, 2005;Jervis et al, 2012).…”