Location: Pest Management ResearchTitle: Molecular genetic and hybridization studies of Diorhabda spp. released for biological control of tamarix) Author
Submitted to: Invasive Plant Science and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/27/2012
Publication Date: 1/2/2013
Publication URL: http://handle.nal.usda.gov/10113/56110
Citation: Bean, D., Kazmer, D.J., Gardner, K., Thompson, D., Reynolds, B., Keller, J.C., Gaskin, J.F. 2013. Molecular genetic and hybridization studies of Diorhabda spp. released for biological control of tamarix. Journal of Invasive Plant Science and Management. 6(1): 1-15. Interpretive Summary: The tamarisk beetle Diorhabda is an effective biocontrol agent for use against tamarisk (Tamarix spp.), an invasive shrub in western North America. Recent work showed that leaf beetle was actually five different species, four of which have been used in the biocontrol program and are the subject of these studies. The change in species names is verified here using DNA and hybridization studies. Hybridization between the four species yielded viable eggs but viability was significantly lower than achieved with crosses within a species. This information will help us track which tamarisk beetle species are being successful in the field at controlling invasive tamarisk, and allow us to estimate which species may hybridize and how that may affect their use as control insects.
Technical Abstract: The tamarisk beetle Diorhabda spp. (Coleoptera: Chrysomelidae) native to Asia and the Mediterranean Basin, is an effective biocontrol agent for use against tamarisk (Tamarix spp.) an invasive shrub in western North America. The genus Diorhabda was recently revised, using morphological characters, into five tamarisk-feeding species, four of which have been used in the biocontrol program and are the subject of these studies. The taxonomic revision is here corroborated using molecular genetic and hybridization studies. Four Diorhabda species separated into five clades using COI sequence data with D. elongata separating into two clades. AFLP analysis using genomic DNA revealed only four clades which corresponded to the four morphospecies. Hybridization between the four species yielded viable eggs in F1 crosses but viability was significantly lower than achieved with intraspecific crosses. Crosses involving D. carinulata (Desbrochers) and the other three species resulted in low F2 egg viability, while crosses between D. elongata (Brullé), D. sublineata (Lucas) and D. carinata (Faldermann) resulted in > 40% F2 egg viability. Crosses between D. carinulata and the other three species resulted in high mortality of D. carinulata females due to genital mismatch. AFLP patterns combined with PCOA gave good separation between D. elongata and D. sublineata, providing a method to measure genetic introgression in the field.