IS THE GLASSY-WINGED SHARPSHOOTER PARASITOID GONATOCERUS ASHMEADI (HYMENOPTERA: MYMARIDAE) ONE SPECIES OR A COMPLEX OF MORPHOLOGICALLY INDISTINGUISHABLE SIBLING SPECIES?

• Author(s): Hoddle, Mark; Stouthamer, R; Triapitsyn, Serguei; Vickerman, Danel;
• Abstract: Gonatocerus ashmeadi Girault (Hymenoptera: Mymaridae) is a common and seemingly widespread egg parasitoid of glassy-winged sharpshooter (GWSS). Location records for G. ashmeadi indicate its natural range to be the southeastern USA and northeastern Mexico (which coincides with the presumed native range of GWSS), and possibly southern and central California (the adventive range of GWSS). G. ashmeadi was collected in California from eggs of the native smoke-tree sharpshooter, Homalodisca literata Ball, as well as from GWSS eggs before G. ashmeadi releases began as part of an organized biological control program and was therefore thought to be native to California. However, the earliest G. ashmeadi specimen from California that we found after a search of the Entomology Museums at UC Davis, Berkley and Riverside, the San Diego Natural History Museum, California Department of Food and Agriculture, USNM and the California Academy of Sciences sources, is from Riverside County in 1978 (first identified by Huber 1988). The purpose of our work is to determine whether G. ashmeadi in the USA and northeastern Mexico is one species or a complex of cryptic species that cant be separated on the basis of currently employed morphological characters. We used three approaches to determine the species identity of different G. ashmeadi populations: (1) reassessment of key morphological features using scanning electron microscopy (SEM) to determine if subtle morphological differences exist between G. ashmeadi populations which could indicate species differences; (2) mating compatibility studies to determine if different populations of G. ashmeadi are reproductively isolated, or if mating occurs, whether offspring are viable thereby defining species groups on the basis of successful interbreeding; (3) to determine if molecular differences exist between G. ashmeadi populations collected from different regions by comparing mitochondrial and ribosomal DNA sequences. Results from these three areas (morphology, behavior, and DNA sequences) have been evaluated together, leading us to the conclusion that G. ashmeadi as it is currently viewed is a valid species and not an aggregate of morphologically indistinguishable cryptic species.
• Publication Date: Aug 2003
• Journal: 2003 Pierce's Disease Research Symposium