Evidence for a recent horizontal transmission and spatial spread of W olbachia from endemic R hagoletis cerasi ( D iptera: T ephritidae) to invasive R hagoletis cingulata in E urope

Abstract

The widespread occurrence of W olbachia in arthropods and nematodes suggests that this intracellular, maternally inherited endosymbiont has the ability to cross species boundaries. However, direct evidence for such a horizontal transmission of W olbachia in nature is scarce. Here, we compare the well‐characterized W olbachia infection of the E uropean cherry fruit fly, R hagoletis cerasi , with that of the N orth A merican eastern cherry fruit fly, R hagoletis cingulata , recently introduced to E urope. Molecular genetic analysis of W olbachia based on multilocus sequence typing and the W olbachia surface protein wsp showed that all R . cingulata individuals are infected with w Cin2 identical to w Cer2 in R . cerasi . In contrast, w Cin1, a strain identical to w Cer1 in R . cerasi , was present in several E uropean populations of R . cingulata , but not in any individual from the U nited S tates. Surveys of R . cingulata from G ermany and H ungary indicated that in some populations, the frequency of w Cin1 increased significantly in just a few years with at least two independent horizontal transmission events. This is corroborated by the analysis of the mitochondrial cytochrome oxidase II gene that showed association of w Cin1 with two distinct haplotypes in G ermany, one of which is also infected with w Cin1 in H ungary. In summary, our study provides strong evidence for a very recent inter‐specific W olbachia transmission with a subsequent spatial spread in field populations.

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