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Research focuses on vital digger bee pollination

A new digger bee research grant is aimed at helping protect this important pollinator by providing land managers with crucial information on its nesting requirements.

University of California scientists from the Davis and Riverside campuses, teaming with SaveNature.Org, an international conservation organization, have received a grant from the Disney Worldwide Conservation Fund to study digger bee pollination ecology and conservation.

The grant, spearheaded by evolutionary ecologist Leslie Saul-Gershenz of the UC Davis Department of Entomology and co-founder of SaveNature.Org, "will help to protect this important pollinator by providing land managers with crucial information on its nesting requirements, to help reduce the impacts from land development and high-impact recreational use," she said.

"Our work will focus on species from the bee species-rich Mojave Desert ecosystem to the coastal dunes in Oregon," said Saul-Gershenz, a Ph.D. student in the Neal Williams pollination ecology lab at UC Davis and a co-founder and research scientist with SaveNature.Org, a San Francisco-based international conservation organization that works collaboratively to protect ecosystems throughout the world.

Saul-Gershenz researches a species of digger bee, Habropoda pallida, a solitary ground-nesting bee, and its nest parasite, a blister beetle, Meloe franciscanus. The researchers also will study the mechanisms that "mediate the interaction between digger bees and a wide-ranging nest parasite known to parasitize multiple pollinator species," she said. "Such information could help to mitigate potential impacts on important pollinators."

Co-principal investigators of the $24,000 one-year grant are evolutionary ecologist/native pollinator specialist Neal Williams, assistant professor in the UC Davis Department of Entomology, and chemical ecologist Jocelyn Millar, professor of entomology at UC Riverside.

SaveNature.Org, co-founded in 1988 by Saul-Gershenz and Norman Gershenz, aims to preserve habitats, protect endangered species, and foster youth connections to nature to ensure that future generations can enjoy wildlife and wild places, Saul-Gershenz said. It has raised more than $3.9 million to help preserve habitat around the world.

Saul-Gershentz and Jocelyn Millar published their blister beetle/digger bee research, "Phoretic Nest Parasites Use Sexual Deception to Obtain Transport to their Host's Nest," in the Proceedings of the National Academy of Sciences (PNAS, 2006).

The Saul-Gershenz/Millar work, considered groundbreaking in the insect order, involves how the larva of the parasitic blister beetle produce a chemical cue or a pheromone similar to that of a female solitary bee to lure males to the larval aggregation. The larva attach to the male bee and then transfer to the female during mating. The end result: the larva wind up in the nest of a female bee, where they eat the nest provisions and likely the host egg.

The PNAS abstract: "Cooperative behaviors are common among social insects such as bees, wasps, ants, and termites, but they have not been reported from insect species that use aggressive mimicry to manipulate and exploit prey or hosts. Here we show that larval aggregations of the blister beetle Meloe franciscanus, which parasitize nests of the solitary bee Habropoda pallida, cooperate to exploit the sexual communication system of their hosts by producing a chemical cue that mimics the sex pheromone of the female bee. Male bees are lured to larval aggregations, and upon contact (pseudocopulation) the beetle larvae attach to the male bees. The larvae transfer to female bees during mating and subsequently are transported to the nests of their hosts. To mimic the chemical and visual signals of female bees effectively, the parasite larvae must cooperate, emphasizing the adaptive value of cooperation between larvae. The aggressive chemical mimicry by the beetle larvae and their subsequent transport to their hosts' nests by the hosts themselves provide an efficient solution to the problem of locating a critical but scarce resource in a harsh environment."

Art of Deception

The research led Pulitzer Prize-winning author Natalie Angier to feature their work in "The Art of Deception," published in the August 2009 edition of the National Geographic magazine. Most recently, U. S. Department of Agriculture (USDA) Forest Service entomologist Michael Ulyshen, writing for the Journal of Natural History, mentioned their work in "Bugback Riding: Transportation for the Masses" (September 2011).

Saul-Gershentz became interested in the subject while a graduate student at San Francisco State University. She wrote "Beetle Larvae Cooperate to Mimic Bees" in the journal Nature (2000).

Of her newest grant, she says: "Our preliminary data show that the blister beetle exploits four other native California bees including important pollinators in the genus Habropoda and Anthophora." Historically, M. franciscanus was known to be a nest parasite of Anthophora edwardsii distributed throughout California.

Her scientific research has taken her all over the world, including Belize, Borneo, Brazil, Costa Rica, Ecuador, Ghana, Madagascar, Namibia, Nepal, Panama, Papua New Guinea, Peru, Tanzania, Trinidad, Thailand and Trinidad. In addition to meloids (blister beetles), bees and pollination ecology, she has studied katydids.

Saul-Gershenz is a past president of the Pacific Coast Entomological Society; in 1991 she became the first female president in its 91-year history. Her images of insects and plants are showcased iin museums and published in a number of documentaries and books. She served as a scientific advisor for Sir David Attenborough's BBC nature documentary "Life in the Undergrowth" and contributed images for his book (Princeton University Press) by the same name. Her research is highlighted in "The Other Insect Societies" (Harvard University Press) and the "Insect Cuticular Hydrocarbons: Biology, Biochemistry and Chemical Ecology" (Cambridge University Press). Her research is summarized in Laurence Packer's newly published book (2010) "Keeping the Bees: Why All Bees Are at Risk and What We Can Do to Save Them" (Harper Collins/Canada).

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