Divergence and evolution of reproductive barriers among three allopatric populations of R hagoletis cingulata across eastern North America and Mexico

Abstract Geography is often a key factor facilitating population divergence and speciation. In this regard, the geographic distributions of flies in the genus R hagoletis ( D iptera: T ephritidae) in temperate North America have been affected by cycles of Pleistocene glaciation and interglacial periods. Fluctuations in climatic conditions may have had their most dramatic effects on geographically isolating R hagoletis flies in the central highland region of M exico. During past periods of allopatry, a degree of post‐zygotic reproductive isolation appears to have evolved between hawthorn‐infesting populations of R hagoletis pomonella ( W alsh) in the central Eje Volcanico Trans Mexicano ( EVTM ) and those from the Sierra Madre Oriental Mountains ( SMO ) of Mexico, as well as hawthorn flies from the eastern USA. Here, we investigate the generality of this finding in the genus R hagoletis by testing for reproductive isolation among populations of R hagoletis cingulata ( L oew) ( D iptera: T ephritidae) collected from infested domesticated sweet cherry ( P runus avium L.) in the USA and black cherry [ P runus serotina E hrh. (both R osaceae)] from the SMO and EVTM . We report evidence for marked post‐mating reproductive isolation among certain R . cingulata populations. The high levels of reproductive isolation were observed between R . cingulata flies from populations in the USA and SMO differed from the pattern seen for R . pomonella , primarily involving the EVTM . In addition, egg hatch was significantly reduced for crosses between SMO males and EVTM females, but not greatly in the opposite direction. We discuss potential causes for the different patterns of post‐mating reproductive isolation among R hagoletis flies.