Population Genetics of the Blueberry Gall Midge, Dasineura oxycoccana (Diptera: Cecidomyiidae), on Blueberry and Cranberry and Testing Invasion Scenarios

SIMPLE SUMMARY: The blueberry gall midge—Dasineura oxycoccana (Johnson) (Diptera: Cecidomyiidae)—is an economically important insect pest of blueberry and cranberry in its native range (USA and Canada) as well as in other parts of the world. This pest was recently introduced and spread through other regions within North America as well as in Europe and Asia, e.g., Korea. To confirm that incipient speciation might have occurred in D. oxycoccana populations associated with blueberry and cranberry as previously reported, it is necessary that approaches on population genetics are performed with a larger sample size. To identify possible routes of worldwide introductions, it is important to trace the source and invasion process of the Korean population. Therefore, we compared the population genetic structure between D. oxycoccana populations from blueberry and cranberry from USA and Korea. We found (1) a clear separation between the two host-associated D. oxycoccana populations from blueberry and cranberry, which could be considered distinct species; (2) the occurrence of five genetically isolated D. oxycoccana subgroups from blueberry; (3) that multiple D. oxycoccana introductions likely occurred in Korea; and (4) that the dominant invasive D. oxycoccana population from Korea was likely introduced from a genotypically diverse population, which was likely introduced from an unsampled source population rather than directly from its native range. ABSTRACT: We compared the population genetic structure between populations of the blueberry gall midge—Dasineura oxycoccana (Johnson) (Diptera: Cecidomyiidae)—from blueberry and cranberry and determined the genetic relationships among geographical subgroups by genotyping 632 individuals from 31 different populations from their native USA regions (New Jersey, Michigan, and Georgia) and from invaded Korean regions using 12 microsatellite loci. Our population genetic analyses showed a clear separation between the two host-associated D. oxycoccana populations from blueberry and cranberry. Using data from only the blueberry-associated D. oxycoccana populations, we identified five genetically isolated subgroups. An analysis of the approximate Bayesian computation suggests that the invasive D. oxycoccana population from Korea appears to have been introduced from an unsampled source population rather than directly from its native range. Our findings will allow for an easier identification of the source of D. oxycoccana into newly invaded regions, as well as to determine their association with blueberry and cranberry, which based on our results can be considered as two distinct species.