The size‐number trade‐off in clonal broods of a parasitic wasp: responses to the amount and timing of resource availability

Abstract

Summary1. Life-history traits that shift in response to environmental conditions are well studied; however, allocation patterns of traits in the context of a trade-off shifting with the environment are hardly examined. 2. Using a polyembryonic parasitoid wasp system, we revealed features of the plasticity in allocation by observing the trade-off outcome between individual body mass and the number of offspring in a wasp brood in response to different host conditions. 3. We manipulated food availability to the host caterpillar at two different phases of development: early host instars during wasp embryo division and late host instars after completion of wasp embryo division. The food manipulation allowed us to shift the rate of development and the total mass of the wasp brood both separately and together through altered host development time and final size. 4. With greater host mass, the trade-off relationship between wasp body mass and brood size shifted, to the same extent for both sexes, towards higher wasp brood size and individual body mass. On the other hand, with faster host development, the trait combinations shifted towards greater wasp body mass but smaller brood size along the same trade-off relationship. 5. These shifts indicate a reduction of wasp brood size when resource level is reduced late in host development. This adjustment yields wasp brood size and body mass in rough proportion to each other and positively related to resource availability late in development. 6. Our demonstration of simultaneous shifts in traits under the trade-off relationship indicates that wasp broods respond differently to the different environmental conditions by altering body mass and the number of wasp individuals, suggesting that the plastic response in the trade-off allocation pattern may be adaptive.

Effects of resource variation during early life and adult social environment on contest outcomes in burying beetles: a context-dependent silver spoon strategy?

“…Recent studies have demonstrated the importance of the timing of nutritional deprivation on success in adulthood [19,20], which may have independent or interactive effects on the expression of adult phenotypes. Distinct stages may often exist in the developmental processes of organisms when nutritional variation has disproportionately large effects on phenotypic expression [21], including effects on disease susceptibility in later life [22] and adaptive polyphenisms, such as the winged phase switch in pea aphids, Acyrthosiphon pisum [23] or horn elongation in dung beetles, e.g.…”

Allocation tradeoffs and life histories: a conceptual and graphical framework

“…1. An example of each tradeoff component, based on studies of a parasitoid wasp exploiting its host (Saeki et al 2009, Crowley and Saeki 2009, Saeki and Crowley 2012, 2013), is shown to the right of each component. The constraint is the amount or supply rate of the limiting resource (e.g.…”

“…As a polyembryonic parasitoid, C. bakeri produces large clonal broods, permitting precise, sex‐specific assessment of the tradeoff. In Saeki et al (2009) and Saeki and Crowley (2013), most components and relationships of Fig. 1 were measured for both sexes and in different environments (Saeki and Crowley 2012, 2013).…”

“…In Saeki et al (2009) and Saeki and Crowley (2013), most components and relationships of Fig. 1 were measured for both sexes and in different environments (Saeki and Crowley 2012, 2013). The role of selection was addressed in a preliminary model (Crowley and Saeki 2009) and is the focus of work in progress (PHC, Paul Ode and Éric Wajnberg).…”

The size‐number trade‐off and components of fitness in clonal parasitoid broods

“…The mechanisms underlying these determinations of brood size and body size have been examined during the preemergence interval Saeki & Crowley, 2012, 2013). Our previous work showed flexible shifts in both brood size and body mass depending on host quality, whereas female-biased sexual size dimorphism was robust.…”