Collaborative Research: The Evolutionary Transition From Solitary to Gregarious Development in Parasitoid Wasps

Collaborative Research: The evolutionary transition from solitary to gregarious development in parasitoid wasps.

Paul Ode1, James Whitfield2, and George Heimpel3

1North Dakota State University

2University of Illinois at Urbana-Champaign

3University of Minnesota-Twin Cities

Abstract:

The study of clutch size is one of the oldest and most productive fields in behavioral ecology and life history theory. A central theme is the conflict between parents and offspring over the allocation of limiting resources and optimal clutch size. Parasitic wasps (parasitoids) have been favored organisms for clutch size studies because their hosts represent well-defined resources on which offspring develop. Parasitoids are classified as solitary if only one, typically siblicidal, larva completes development per host or gregarious if more than one non-siblicidal offspring develops per host. Phylogenetic patterns suggest that solitary development is ancestral to gregariousness and that this transition has occurred many times. Population genetic models suggest the conditions favoring the spread of non-siblicidal behavior are stringent but may be relaxed if one or more of the following factors occur: sex allocation behaviors increase within brood relatedness, loss of larval mobility, acquisition of the ability to distinguish relatives from non-relatives, inbreeding, or reduced superparasitism. While the phylogenetic relationships of most parasitoid taxa are not well understood, the well-studied phylogeny of the braconid genus Cotesia allows detailed study of whether the aforementioned factors were associated with the evolution of gregariousness within this genus. Collection of DNA sequences from additional Cotesia species will further strengthen the phylogeny. Behavioral studies will assess the role of siblicide, mobility, sex allocation, and kin-discrimination in the evolution of gregariousness. Field and laboratory studies will determine the effects of inbreeding and superparasitism on the evolution of gregariousness.