In British Columbia, Canada, Dasineura oxycoccana Johnson (Diptera: Cecidomyiidae) was initially found on highbush blueberry, Vaccinium corymbosum L. (Ericaceae) and has recently become a pest of cranberry, Vaccinium macrocarpon Aiton, a crop that is often found in close proximity with blueberry. Previous work has shown no temporal isolation and a potential for gene flow between these two D. oxycoccana populations. However, important behavioural differences were observed suggesting the potential for host races or cryptic species. Host races and cryptic species differ in their degree of assortative mating and reproductive isolation from partial to complete. We assessed whether populations of adult D. oxycoccana on these two crops would discriminate against mates from different natal hosts. Mating experiments were conducted within the greenhouse in 2010 using small glass vials without host plants present. Our results show D. oxycoccana from cranberry and blueberry hosts displayed complete assortative mating in the absence of their host plants. Behavioural data collected from the different crosses suggest these two D. oxycoccana populations differ in sex pheromones and close-range 'courtship pheromones'. We conclude that D. oxycoccana populations on cranberry and blueberry in British Columbia are reproductively isolated and probably represent cryptic species.

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Dasineura oxycoccana (Johnson) (Diptera: Cecidomyiidae) is a pest of cranberry, Vaccinium macrocarpon (Aiton) (Ericales: Ericaceae), and highbush blueberry, Vaccinium corymbosum (L.) (Ericales: Ericaceae), in North America. In British Columbia, Canada, D. oxycoccana was first found on highbush blueberry in 1991 and then on cranberry seven years later. Because many cranberry and highbush blueberry farms are adjacent to one another, we hypothesized that D. oxycoccana was moving from highbush blueberry onto cranberry. Cranberry and highbush blueberry differ in phenology, and adaptation to these different phenologies may result in host races or cryptic species on these two crops. We recognized the alternative hypothesis that D. oxycoccana had arrived as immature stages with cranberry vines imported from another region of North America. During spring and summer, we recorded the phenology of D. oxycoccana and the development of plant shoots from three cranberry and three highbush blueberry farms to determine whether the opportunity exists for successful movement of D. oxycoccana between the two crops. Our results show that D. oxycoccana from cranberry and highbush blueberry overlap in phenology for much of the season, indicating a high potential for movement and gene flow. However, differences were seen in number of larvae per shoot, location of pupae, and heat unit accumulation during larval development suggesting that instead there may be the potential for host race or cryptic species formation.