Evidence for a recent horizontal transmission and spatial spread ofWolbachiafrom endemicRhagoletis cerasi(Diptera:Tephritidae) to invasiveRhagoletis cingulatainEurope

Abstract

The widespread occurrence of Wolbachia 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 Wolbachia in nature is scarce. Here, we compare the well-characterized Wolbachia infection of the European cherry fruit fly, Rhagoletis cerasi, with that of the North American eastern cherry fruit fly, Rhagoletis cingulata, recently introduced to Europe. Molecular genetic analysis of Wolbachia based on multilocus sequence typing and the Wolbachia surface protein wsp showed that all R. cingulata individuals are infected with wCin2 identical to wCer2 in R. cerasi. In contrast, wCin1, a strain identical to wCer1 in R. cerasi, was present in several European populations of R. cingulata, but not in any individual from the United States. Surveys of R. cingulata from Germany and Hungary indicated that in some populations, the frequency of wCin1 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 wCin1 with two distinct haplotypes in Germany, one of which is also infected with wCin1 in Hungary. In summary, our study provides strong evidence for a very recent inter-specific Wolbachia transmission with a subsequent spatial spread in field populations.

Diversity and evolution of the Wolbachia endosymbionts of Bemisia (Hemiptera: Aleyrodidae) whiteflies

“…The double infection of Wolbachia supergroups B and O in the same population indicates horizontal transmission of Wolbachia . Horizontal transmission of Wolbachia has often been speculated based on phylogenetic analysis (Werren et al 1995a; Sintupachee et al 2006; Stahlhut et al 2010; Schuler et al 2013; Zhang et al 2013). Wolbachia has also been reported from other whitefly genera such as Trialeurodes and some parasitoids (Raychoudhury et al 2009; Cass et al 2014), and this diversity of distribution may also hint horizontal transmission.…”

Cytogenetic and symbiont analysis of five members of the B. dorsalis complex (Diptera, Tephritidae): no evidence of chromosomal or symbiont-based speciation events

“…More importantly, it is a well-documented example of the implication of Wolbachia in restriction in gene flow and enhancement of incompatibility between natural populations of the species (Riegler and Stauffer 2002). Other Rhagoletis species that seem to have persistent and multiple strain infections (although less populations are studied) are Rhagoletis pomonella (Schuler et al 2011) and Rhagoletis cingulata (Drosopoulou et al 2011a, Schuler et al 2013), along with some Rhagoletis species of Japan (Coats et al 2013). Outside Rhagoletis , the only species demonstrating persistent Wolbachia infections is Anastrepha fraterculus , (Selivon et al 2002, Cáceres et al 2009, Coscrato et al 2009, Marcon et al 2011, Martinez et al 2012).…”

Scientific Opinion on the pest categorisation ofRhagoletis cingulata(Loew)

“…Concerning detection and identification at the place of production, as mentioned in section 3.4.2, R. cingulata has the same host species as R. cerasi, which is phylogenetically distant and belongs to a different species group, but is native to Europe (Schuler et al, 2013). Therefore, unless care is taken in identifying the fruit flies attacking European cherry crops, outbreaks of R. cingulata may be overlooked.…”

“…In the risk assessment area, however, R. cingulata mainly infests sour cherries and wild sweet cherries, which are grown in most of the MSs for fruit production (Table 4). These two crop species are also hosts of the native European cherry fruit fly (R. cerasi) (Schuler et al, 2013) spreading and has a considerable potential to expand its distribution in Europe. Among the other factors influencing establishment are the high reproductive potential, the high infestation levels (reaching more than 20 %), the survival of its pupae that emerge the following year and its capacity to adapt to different environments (CABI, 2014a).…”