Temporal Variation in the Structure of a Gall Wasp Assemblage along a Genetic Cline of Quercus crispula (Fagaceae)

Abstract

I examined temporal variations in the structure of a gall wasp assemblage along a genetic cline among 12 half-sib families (HSFs) of the host oak Quercus crispula, by comparing patterns in the species composition, species richness, and abundance of component species of the assemblage in 2 years. Three of 14 gall sorts were dominant in both years (common gall wasps), and 3 dominated in only one of the years (opportunistic gall wasps). Species composition reflected the genetic cline among HSFs, and differed between years. However, the relative similarity of species composition across HSFs did not vary between years. The mean species richness differed among HSFs, but the relative richness across HSFs did not differ between years. Two of the common gall wasps showed similar, significant responses to the genetic cline between years, whereas the opportunistic gall wasps showed relatively generalist responses. Thus, the overall structure of the assemblage along the genetic cline was characterized mainly by the common gall wasps, whereas the temporal variation was caused additively by the opportunistic gall wasps. The lack of HSF versus year interactions suggests that the effects of plant genetics on this assemblage were not masked by environmental interactions.