Host‐associated differentiation in reproductive behaviour of cecidomyiid midges on cranberry and blueberry

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.