Ecological speciation via host-shifting is often invoked as a mechanism for insect diversification, but the relative importance of this process is poorly understood. The shift of Rhagoletis pomonella in the 1850s from the native downy hawthorn, Crataegus mollis, to introduced apple, Malus pumila, is a classic example of sympatric host race formation, a hypothesized early stage of ecological speciation. The accidental human-mediated introduction of R. pomonella into the Pacific Northwest (PNW) in the late-1970’s allows us to investigate how novel ecological opportunities may trigger divergent adaptation and host race formation on a rapid timescale. Since the introduction, the fly has spread in the PNW, where in addition to apple, it now infests native black hawthorn, C. douglasii, and introduced ornamental hawthorn, C. monogyna. We use this “natural experiment” to test for genetic differentiation among apple, black and ornamental hawthorn flies co-occurring at three sympatric sites. We report evidence that populations of all three host-associations are genetically differentiated at the local level, indicating that partial reproductive isolation has evolved in this novel habitat. Our results suggest that conditions suitable for initiating host-associated divergence may be common in nature, allowing for the rapid evolution of new host races when ecological opportunity arises.  

These data are genotypes for 28 microsatellite loci (originally described in Velez et a. 2005, Molecular Ecology Resources) for Rhagoletis flies collected from three different host associations (apple- Malus pumila, black hawthorn - Crataegus douglasii, and ornamental hawthorn - Crateagus monogyna) in each of three different sympatric sites Washington State University, Burnt Bridge Creek Greenway, and St. Cloud Park. Details about collection locations, host-plant associations, and insect collection and rearing methods can be found in the associated manuscript.

DNA extraction, PCR conditions including primer pairs, genotyper conditions (using a Beckaman-Coulter CEQ 8000), and allele calling protocols are described in the associated manuscript.  

Genotypes are provided in the "Convert" format, which allows for easy file conversion for different population genetics software formats using PGDSpider (http://www.cmpg.unibe.ch/software/PGDSpider/).

Population designations are as follows:

Missing data are indicated with "?"