Introduced biological control agents are often collected as relatively small subpopulations that may not represent the full genetic diversity of the source population. Does population structuring or decreased genetic diversity affect the efficiency of these introduced biological control agents? Our research is concentrating on addressing this issue using Spurgia esulae, a gall midge introduced as a biological control agent of leafy spurge (Euphorbia esula). E. esula was introduced into the United States in the early 1800’s and has since become a noxious rangeland weed in the Northern Great Plains. In 1986 S. esulae was imported from Italy and has become established in North Dakota, Wyoming and Montana. The goal of our research is to determine why certain leafy spurge genotypes are susceptible to the fly whereas others are very resistant. It may be that limited genetic variability of the fly or specialization of genetically structured native fly populations on certain genotypes are involved. Preliminary data using ISSR (Inter Simple Sequence Repeat) markers indicate that there are genetic differences between S. esulae populations collected from the original source population in Italy and populations established in the US. Here we present data from microsatellite loci to get a closer look at the differences among populations. This research is part of a larger project that involves testing gall midge preference and performance for different leafy spurge genotypes and exploring whether the introduced gall midge has adapted to the leafy spurge populations in North America.
Species 1: Diptera Cecidomyiidae Spurgia esulae (leafy spurge tip gall midge)
Species 2: Euphorbiales Euphorbiaceae Euphorbia esula (leafy spurge)
Keywords: biological control
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