Submitted to: Zootaxa
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 4, 2009
Publication Date: May 11, 2009
Citation: Tracy, J.L., Robbins, T.O. 2009. Taxonomic revision and biogeography of the Tamarix-feeding Diorhabda elongata (Brulle, 1832) species group (Coleoptera: Chrysomelidae: Galerucinae: Galerucini) and analysis of their potential in biological control of Tamarisk. Zootaxa. 2101:1-152. Interpretive Summary: The leaf beetle Diorhabda elongata and its sibling (similar appearing) species are important as current and potential biological control agents for exotic and invasive tamarisk or saltcedar (Tamarix spp.) in the western United States. Taxonomists have disagreed on how many sibling species, if any, exist for D. elongata. Knowledge of the native Old World geographic ranges of D. elongata and its sibling species is useful in understanding differences in their potential ranges in North America. In order to stabilize the taxonomy and determine the biogeography of these species, the genitalia (reproductive structures) were studied in over 700 museum specimens from across North Africa, southern Europe and Asia. Five sibling species were found to comprise a new D. elongata species group. Each species has unique biogeographical traits suiting them to different regions invaded by tamarisk in North America. Four species were previously tested and verified as specific feeders of tamarisk, and released in North America under the name D. elongata. Diorhabda carinulata from China and Kazakhstan (old name D. e. deserticola), is successfully suppressing tamarisk over large areas of the Great Basin desert. The true D. elongata is establishing well in California and parts of west Texas and is best suited for Mediterranean habitats. Diorhabda sublineata has potential for the Sonoran and southeastern Chihuahuan deserts. Diorhabda carinata should be best suited for the Great Plains grasslands and the Mojave and northern Chihuahuan deserts. A fifth species, D. meridionalis, may be suited to subtropical maritime deserts, has yet to be safety tested.
Technical Abstract: The primarily Palearctic Diorhabda elongata species group is established for five Tamarix-feeding sibling species (tamarisk beetles): D. elongata (Brullé, 1832), D. carinata (Faldermann, 1837), D. sublineata (Lucas, 1849) REVISED STATUS, D. carinulata (Desbrochers, 1869), and D. meridionalis Berti & Rapilly, 1973 NEW STATUS. Diorhabda koltzei ab. basicornis Laboissière, 1935 and D. e. desericola Chen, 1961 are synonymized under D. carinulata NEW SYNONYMY. Illustrated keys utilize genitalia, including male endophallic sclerites and female vaginal palpi and internal sternite VIII. Distribution, comparative biogeography, biology, and potential in biological control of Tamarix in North America are reviewed. Diorhabda elongata is circummediterranean, favoring Mediterranean and temperate forests of Italy to western Turkey. Diorhabda carinata resides in warm temperate grasslands, deserts, and forests of southern Ukraine south to Iraq and west to Kazakhstan. Diorhabda sublineata occupies Mediterranean woodlands from France to North Africa and subtropical deserts east to Iraq. Diorhabda carinulata primarily inhabits cold temperate deserts of Mongolia and China west to Russia and south to montane grasslands and warm deserts in southern Iran. Diorhabda meridionalis primarily occupies maritime subtropical deserts of southern Pakistan and Iran to Syria. Northern climatypes of D. carinulata are effective in Tamarix biological control, especially in the Great Basin desert. Diorhabda elongata is probably best suited to Mediterranean woodlands of northern California. Northern climatypes of D. carinata may be best suited for central U.S. grasslands. Diorhabda sublineata, D. meridionalis, and southern climatypes of D. carinata and D. carinulata may each be uniquely suited to areas of the southwestern U.S.