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

Abstract

Body size can strongly influence the components of fitness. We investigated the role of body mass in the reproductive success of the parasitoid Copidosoma bakeri (Howard) (Hymenoptera: Encyrtidae). Copidosoma bakeri develops polyembryonically, producing thousands of genetically identical individuals from one egg. In this species, the brood size and body mass of clonal individuals developing within a host are in a trade-off relationship, which flexibly responds to the environment while maintaining female-biased sexual size dimorphism. We addressed the following questions regarding several possible effects of body mass on male and female reproductive success. (1) Is longevity positively related to body size in both sexes? (2) Is potential fecundity positively related to female body size? (3) Is mating competitiveness positively correlated with male body size? We found that body size increased with longevity of females, but not of males. Copidosoma bakeri was weakly synovigenic; a few eggs were produced after female maturation. Also, egg volume increased with age of the females. We did not detect a relationship between body size and potential fecundity, but mated females produced more eggs than unmated females. Thus, larger females may increase their opportunities to mate, find hosts, and oviposit primarily by living longer. Male mating competitiveness was not related to body mass. Mating reduced male longevity, suggesting a cost of mating that was independent of body mass. Differences between males and females in the effects of body mass on longevity suggest sex-specific selection pressures on body mass that may explain female-biased sexual size dimorphism.

Dietary sugars and amino acids increase longevity and enhance reproductive parameters of Bracon cephi and B. lissogaster, two parasitoids that specialise on wheat stem sawfly

“…After death, as an estimate of parasitoid body size (Jervis et al, 2003), we measured the hind tibiae using a Dino‐Lite microscope (model AM7115MZT‐Edge, Dino‐Lite, Hsinchu, Taiwan) at ×50 magnification using the associated computer software (DinoXcope version 1.5.15). These measurements are needed because female size can influence longevity, egg load, and egg volume (Ellers & Jervis, 2003; Jervis et al, 2003; Reis et al, 2019; Saeki & Crowley, 2013).…”

Effects of sucrose supplementation and generation on life‐history traits of Bracon cephi and Bracon lissogaster, parasitoids of the wheat stem sawfly

“…At death, we measured the hind tibia length of the females using a digital micrometre (H‐2780; Mitutoyo, Japan), as a measure of parasitoid body size (Jervis et al ., ). Body size in parasitoids is known to be positively correlated with several key life‐history traits, including longevity, egg load and egg volume (Bezemer & Mills, ; Ellers & Jervis, ; Saeki & Crowley, ).…”

The effect of body size on oviposition success of a minute parasitoid in nature

“…As a result, assumptions of many classic life‐history models remain untested. Under laboratory conditions, parasitoid body size has been shown to increase egg production, longevity, and oviposition rate (Bezemer & Mills, ; Saeki & Crowley, ). However, this does not necessarily translate into higher success in the field.…”