Mitochondrial DNA diversity and Wolbachia infection in the flea beetle Aphthona nigriscutis (Coleoptera: Chrysomelidae): An introduced biocontrol agent for leafy spurge

Abstract

Aphthona nigriscutis is one of several species of Aphthona flea beetles that have been introduced into North America in an effort to control the weed, leafy spurge (Euphorbia esula). It has been a very effective biological control agent at some locations but not at others. Overall genetic diversity is one parameter that could have an effect on Aphthona establishment at specific locations. We have examined the genetic diversity of mitochondrial DNA in populations of A. nigriscutis from several North American collection sites. The results indicate that the insects are divided into two mtDNA clades. About 78% of the individuals comprise a clade (A) that has little or no mtDNA diversity. The remaining insects in the other clade (B) display extensive diversity with 15 haplotypes observed. The two subpopulations coexist at most locations. The bacterial endosymbiont Wolbachia has been discovered in some individuals. About 86% of the individuals from mtDNA clade A tested positive for Wolbachia. Portions of the Wolbachia ftsZ and wspA genes were sequenced and the sequences have been shown to fall within the Wolbachia Supergroup A. None of the insects from clade B appear to be infected. The association of Wolbachia with one, but not both, mtDNA clades of A. nigriscutis may play a role in limiting genetic diversity within beetle populations.