Eastern and western lineages of Leucotaraxis argenticollis (Diptera: Chamaemyiidae), a biological control agent for Adelges tsugae (Hemiptera: Adelgidae), are capable of hybridization in the laboratory.

Abstract

Hybridization between eastern and western lineages of the biological control agent, Leucotaraxis argenticollis (Zetterstedt) (Diptera: Chamaemyiidae), was demonstrated in the laboratory. The western lineage is abundant on hemlock woolly adelgid, Adelges tsugae Annand (Hemiptera: Adelgidae) in western North America while a genetically distinct eastern lineage feeds mostly on pine adelgids (Hemiptera: Adelgidae: Pineus spp.). Western flies have been released in eastern North America but establishment has not been observed. When reared on A. tsugae in the laboratory, many eastern L. argenticollis larvae did not survive, and of those that did reach pupariation, 21% survived to the adult stage. To assess hybridization, eastern females were placed with western males for no-choice mating. They produced hybrid offspring with 8% survival to the adult stage when reared on A. tsugae. Further investigation of hybrid fitness, assortative mating, and the prey-seeking strategies of Leucotaraxis would aid in predicting the outcome of potential hybridization in the field.