Asian lady beetle + microsporidia = Native lady beetle death!

As we've noted before in this blog, the decline of many native lady beetle species occurring in North America and other countries coincides with the presence of the Asian lady beetle, Harmonia axyridis. The mechanisms as to why this is the case have been unclear. Is Harmonia a more effective predator than natives? Is it merely eating the natives at a particular life stage (termed intraguild predation, and the topic of Chelsea's M.S. thesis)? Does it have a faster life cycle and therefore able to reproduce in higher numbers?

A new study published today in Science reports that H. axyridis may be such an effective invasive species due to microsporidia in its hemolymph. These microsporidia are safe for their hosts, but when native species (to Europe), such as Coccinella septempunctata, were injected with these microsporidia they died. In the field, this may mean that consumption of H. axyridis eggs is lethal to intraguild competitors.

C. septempunctata is also established in the U.S., and is a dominant competitor of our own native species. It will be interesting to see how these new findings will influence our understanding of American native lady beetle declines.

Harmonia axyridis (wikipedia) 

Report in Science (paywall): http://www.sciencemag.org/content/340/6134/862

Science Daily article: http://www.sciencedaily.com/releases/2013/05/130516142541.htm

Are you signed up for the Gardiner Lab Buckeye Lady Beetle Blitz training workshop?