Glucose-phosphate isomerase as a gene of major effect in soldier developmental rates within Copidosoma floridanum (Hymenoptera: Encyrtidae)

The polyembryonic parasitoid, Copidosoma floridanum, exhibits a caste system whereby progeny develop into sterile soldiers or reproductive larvae. Female eggs produce large numbers of soldiers for defense against intraspecific and interspecific competitors, with early emerging soldiers defending against the former and later-emerging soldiers defending against the latter. Previous findings suggested timing of soldier emergence may have a strong genetic basis directly affected by the metabolic enzyme, Gpi (glucose-phosphate isomerase). To test this hypothesis, multiple clonal lines were established of C. floridanum homozygous for three Gpi alleles commonly encountered in the southeastern United States. The three alleles were designated as Gpi⁵⁴, Gpi¹⁰⁰ and Gpi¹²⁰ and were used to assay the outcome of competition in a multiparasitized host. Our results indicated soldiers homozygous for Gpi⁵⁴ generally do not emerge from a host simultaneously parasitized by clones homozygous for either Gpi¹⁰⁰ or Gpi¹²⁰. This is due to the finding that Gpi¹⁰⁰ and Gpi¹²⁰ clones produce soldiers at least two hours earlier than Gpi⁵⁴ clones. Taken together, our results indicate that soldier development time varies with Gpi genotype and that this gene significantly affects the outcome of wasp competition.