The use of molecular approaches in biological control: using DNA barcoding to resolve taxonomic ambiguity between geographically distinct populations

The use of molecular approaches in biological control: using DNA barcoding to resolve taxonomic ambiguity between geographically distinct populations
Rosie Mangan1, James C. Carolan2, Jan-Robert Baars1
1BioControl Research Unit, School of Biology and Environmental Science, University College Dublin, Ireland; 2Department of Biology, National University of Ireland Maynooth, Co. Kildare, Ireland

Hydrellia lagarosiphon Deeming, a leaf mining fly species in the family Ephydridae, is currently being investigated as a biological control agent of Lagarosiphon major (Ridl.) Moss ex Wager (Hydrocharitaceae), an invasive aquatic plant found in several European countries as well as New Zealand and Australia. A vital step when considering the natural enemies’ potential for biological control, particularly those new to science, is the ability to accurately identify it.  Genetic assessments are  becoming routine practice in  species  identification, but  there  are  only a  limited number  of biological control programmes that have characterized genetic variation within or among populations of weed biological control agents prior to their release. The target weed L. major is a common aquatic plant in its native range in southern Africa. The fly was first found associated with this plant in 2008 and subsequently found throughout the geographic range of the plant even in areas considered quite isolated. The mitochondrial DNA cytochrome c oxidase subunit I (COI) barcoding sequence was used to determine the level of genetic variation of H. lagarosiphon within and among populations within spatially separated geographical areas of South Africa. The data confirmed that a single leaf-mining species damages L. major plants over a very large area in South Africa. The results also confirm that the individuals used in host specificity testing are from one population and there is an apparent absence of cryptic species. This information can be built on and used to predict the minimum number of individuals needed for release to maintain diversity, which can improve rates of establishment.