04 November 2005
Karner Blue threatened by invasive species?
The Karner Blue (Lycaeides melissa samuelis) is an endangered butterfly endemic to the Great Lakes region, with the largest populations in Michigan and Wisconsin. While other subspecies in the L. melissa complex feed on a variety of plants in the Fabaceae family, the wild lupine, Lupinus perennis, is the only host plant for the Karner Blue, contributing to its rarity.
A new paper in the Journal of the Lepidopterists' Society notes a new larval host plant for the nominate subspecies of Melissa Blue, L. melissa melissa. Colonies in western Wisconsin and eastern Minnesota are feeding on crown vetch, Coronilla varia, an aggressive introduced legume planted for erosion control and slope stabilizations, especially along highways. It is now considered a serious invasive species.
The reason this is so notable is that the rapid spread of crown vetch, in particular along road corridors, provides a means for the Melissa Blue to penetrate into the range of the Karner Blue; in fact, the Melissa Blue is undergoing a range expansion that is facilitated by its new use of crown vetch. The two species are now separated by less than 70 km (~43 miles), including the areas that contain the main part of the Wisconsin population of Karner Blue.
Nobody is certain what will happen when the two species meet, but there is a good chance that they will hybridize and produce viable offspring. This possibility is a huge threat to the existence of Karner Blue as a distinct subspecies.
Dana, R. P., C. Lane, and D. Hansen. 2005. New larval hostplant for Lycaeides melissa melissa in Wisconsin and Minnesota and potential threat to Lycaeides melissa samuelis (Lycaenidae). Journal of the Lepidopterists' Society 59:175-177. Photo public domain, USFWS.