Male Contest Competition and Mating Success in the Parasitoid Wasp Nasonia vitripennis (Pteromalidae)

Abstract

Contest competition is the direct, often aggressive struggle for mates, resources, or both. Contest winners exclude others from access to key, monopolizable resources, and are therefore expected to have the highest mating success. However, contest losers may have higher mating success than expected due to factors such as mate choice and alternative mating phenotypes. Thus, studies explicitly examining contest competition and mating success are needed to fully understand mating systems. Here, I examine factors influencing contest competition, assessment during contests, the link between contest and mating success, and behavioral differences between laboratory strains in Nasonia vitripennis, a model species for parasitoid wasps.

In chapter 1, I examined the effects of size and age on male-male contest competition and whether these effects can be explained by contest theory. I concluded that larger males won contests against smaller males as a result of the larger males' greater fighting ability (resource-holding potential). However, it remains unclear whether old males won contests against young males as a result of old males' valuing matings more highly (resource value).

In chapter 2, I examined whether males engage in size assessment during contests. I found that males persisted in contests based solely on their own size, with no regard for that of their competitor's (pure self-assessment).

In chapter 3, I examined the relationship between contest and mating success when the occurrence of prior competition and the presence of a monopolizable resource were manipulated. I found that the presence of a monopolizable resource affected contest dynamics, and that prior competition influenced male-female interactions. However, contest success did not lead to mating success.

In chapter 4, I examined whether two commonly-used laboratory strains differed in their competitive ability, mating preference, and insemination ability. I found that these strains differed in competitive ability and mating preference, but not in insemination ability.

My studies highlight the complexity of the N. vitripennis mating system and expand our understanding of parasitoid contest competition.