DAVIS — Yellowjackets, which kill or scavenge insects and other protein-rich foods to feed their young, can wreak ecological havoc, says ecologist Erin Wilson of the University of California, Davis.

The Western yellowjacket (Vespula pensylvanica), native to the western United States and first discovered in Hawaii in 1977, is like "a vacuum cleaner" and is clearly a threat to native species in Hawaii, said Wilson, a postdoctoral scholar in the Louie Yang lab, UC Davis Department of Entomology.

Wilson, the lead author of Hawaii-based research published in the current (Nov. 11, 2010) edition of the journal Ecology, will speak on "Yellowjacket Life History Shifts Modify Invasion Impacts in Hawaiian Ecosystems" from 12:10 to 1 p.m. Dec. 1 in 122 Briggs Hall. Her talk, part of the department's fall seminar series and free and open to the public, will be webcast live at http://uc-d.na4.acrobat.com/ucsn1/ and then archived on the entomology website.

"The introduction of non-native organisms is a leading cause of imperilment of native species," said Wilson, who has studied the social wasps at two sites: the Hawaii Volcanoes National Park on the island of Hawaii and the Haleakala National Park on Maui since 2004. The yellowjacket "may seriously threaten endemic invertebrates that evolved in the absence of these social insects," said Wilson, who received her doctorate in ecology last year from UC San Diego.

"Invasive predators affect native species directly and indirectly, and the magnitude of these effects is highly dependent on the history of the recipient community," she said. "Furthermore, the impact of this social wasp may be magnified by apparent shifts in colony structure in the introduced range." Scientists have found that the incidence of perennial or overwintering colonies is higher in Hawaii than in the native range of V. pensylvanica.

Compared to annual colonies, overwintering perennial colonies can collect twice as many prey items and produce 10 times the worker force, Wilson said. Some perennial colonies were huge, the size linked to Hawaii's mild climate and the ability of the yellowjackets to establish perennial colonies. One Maui colony included "as many as 600,000 individuals," she said. In its native range, the typical size is less than a few thousand wasps.

Wilson and her colleagues are interested in pursuing scientific research involving honey bees and yellowjackets. Recent evidence suggests that honey bees play an important role in mediating interactions between native arthropods and invasive yellowjackets. Throughout the season, Vespula wasps will consume not only honey bees but their honey — "so much that honey bee hives may serve as one-stop shopping for hungry social wasps," she said.

"Honey bees may in part subsidize yellowjacket populations, providing resources particularly beneficial to perennial yellowjacket colonies in times when resources are scarce," Wilson said.

More information on her research is on her website at http://vespularesearch.com/. The Ecology article is located at www.esajournals.org/toc/ecol/91/11.