Progeny and Sex Allocation Decisions of the Polyembryonic Wasp Copidosoma floridanum

Abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. British Ecological Society is collaborating with JSTOR to digitize, preserve and extend access to Journal of Animal Ecology. Summary 1. The reproductive biology of the polyembryonic encyrtid wasp Copidosomafloridanum was examined in a series of laboratory experiments and related to observations from field collections. Females laid one or two eggs per host, producing broods comprised of all males, all females, or both sexes (mixed). Each egg produced multiple embryos that developed into either precocious larvae that never became adult or reproductive larvae that developed into reproductive adults. 2. The age of the host-egg when it was parasitized was found to have a substantial effect on offspring clutch sizes and sex ratios. (i) The clutch sizes and overall survivorship of female and mixed broods decreased with increasing host-egg age, whereas male clutch sizes and survivorship were relatively unaffected by host-egg age. (ii) Offspring sex ratios (proportion males) of mixed broods were higher in older hosteggs. (iii) Body sizes of males and females were negatively correlated with clutch size. Larger females had higher fecundities and larger males had greater mating abilities. 3. Host-egg age also affected competitive asymmetries between males and females. In young host-eggs, female precocious larvae were much more abundant than males and were instrumental in reducing the number of males in mixed broods. In older host-eggs, the numbers of male and female precocious larvae were much lower, and were approximately equal. As a result, sex ratios of mixed broods in older host eggs were closer to equality. 4. Ovipositing females responded to host-egg age and host encounter rates when making oviposition decisions. Females laid more female eggs in younger hosts and more mixed broods in older hosts. Females laid more mixed broods when encounter rates were low and more female broods when encounter rates were high.

Caste determination in a polyembryonic wasp involves inheritance of germ cells

“…The evolutionary mechanism driving these changes is likely natural selection because functional studies indicate that C. floridanum broods suffer significant fitness costs when soldiers are absent or too few reproductive larvae are produced (25)(26)(27)(28)50). In contrast, the developmental mechanisms regulating proliferation and asymmetric inheritance of germ cells by embryos in a brood are unclear.…”

Balancing the Size-Number Tradeoff in Clonal Broods

“…In the absence of suitable data from C. bakeri, we estimated the data for tibia length vs egg load for female C. floridanum at eclosion from Fig. (5A) of Ode and Strand (1995). We then took logarithms of both variables and conducted a model II regression to estimate the slope and 95% confidence interval.…”

Host resistance and the evolution of kin recognition in polyembryonic wasps

“…Female wasps produce all-male or all-female broods by laying one egg per host and mixed broods by laying two (one male and one female) (Strand 1989). The number of reproductive progeny per host are similar between brood types, but female eggs produce many soldiers whereas male eggs produce almost none (Ode & Strand 1995). This asymmetry in soldier development probably evolved because of the mating structure of C. floridanum populations.…”