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New Fly Species Formed Through Hybridization - July 2005
July 27, 2005
UNIVERSITY PARK, Pa., -- Researchers at Penn State recently discovered a new hybrid-origin fruit fly and documented their findings in the July 28th issue of Nature.
According to Dietmar Schwarz, postdoctoral scholar in the entomology at Penn State, the Lonicera Fly is a newly discovered fruit fly population within the Rhagoletis pomonella species group. "The Lonicera Fly is an independent population that arose by hybridization between two native fruit fly species," says Schwarz. "This type of speciation, called homoploid hybrid speciation, is one in which two different species give rise to a third without a change in chromosome number. It has always been regarded as theoretically possible but very rare. Our research indicates that it does indeed occur, and may occur in animals much more frequently than originally thought," Schwarz explains.
Homoploid hybrid speciation is well documented in plants, but in animals it faces two obstacles. Hybrids have to be reproductively isolated and occupy a separate ecological niche in order to form an independent population. In 1997, the researchers discovered the infestation of the Lonicera Fly on non-native brushy honeysuckle forms. Schwarz worked with his then advisor, Bruce McPheron, professor of entomology and associate dean for research at Penn State's College of Ag Sciences, and two other Penn State students to determine how this fruit fly developed. They discovered the honeysuckle, an invasive weed abundant throughout the northeastern US, was a host to a fruit fly that showed a unique mixture of characteristics of two native fruit flies, the blueberry maggot (R. mendax) and the snowberry maggot (R. zephyria). "This suggests that the infestation of the honeysuckle is the unique result of both hybridization and a recent host shift in a host specific animal, the fruit fly," says Schwarz. He theorizes the host shift to honeysuckle freed the Lonicera Fly from competition with the parent species and provided a mechanism for reproductive isolation.
As a result of their work, Schwarz says he hopes to reduce the bias against hybridization as an evolutionary force in zoology and that it will be considered as a viable hypothesis for the origin of other host-specific animals. "We predict that future studies will discover more populations with Lonicera Fly-like evolutionary histories," Schwarz reports.
Schwarz started his work on the Lonicera Fly as a graduate student in entomology at Penn State and was the topic of his Ph.D. thesis. Continuing research was funded by National Science Foundation grant (Ecologically Mediated Hybrid Speciation in Rhagoletis). For full results of the study, contact Schwarz at (814) 863-0102 or by e-mail at dxs332@psu.edu.
Established in 1963, Penn State's Department of Entomology has grown into a well-balanced department providing undergraduate education, graduate student training and extension outreach education. Twenty faculty and more than thirty graduate students work on a variety of research topics. The department is part of Penn State's College of Agricultural Sciences. For more information, contact the department at (814) 865-1895 or visit the department's Web site at http://www.ento.psu.edu/.