Abstract
The brown marmorated stink bug Halyomorpha halys (Stål) is a globally invasive species that harbours the primary bacterial symbiont ‘Candidatus Pantoea carbekii’. In this work, P. carbekii was used as another genetic marker to investigate the biodiversity and biogeographical patterns of this important pest, in native and newly invaded areas, especially in Italy. The correlation between the genetic structure of the symbiont and that of its host was studied through the analyses of one bacterial and one host marker, the putative pseudogene ΔybgF and the mitochondrial gene COI, respectively. As a result, five new P. carbekii haplotypes were identified, and an association pattern between host-symbiont haplotypes was observed. Host species showed higher haplotype diversity than symbiont, which can be expected in a long term host-symbiont association. Populations from the north-eastern Italy showed the highest values of genetic diversity for both markers, highlighting that this particular Italian area could be the result of multiple ongoing introductions. Moreover, some of the symbiont-host haplotypes observed were shared only by populations from north-eastern Italy and native areas, especially Japan, suggesting further introductions from this native country to Italy. Overall, our findings improve the understanding of the potential origin of multiple accidental introductions of H. halys in Italy.
Highlights
Especially primary or obligatory symbionts (p-symbionts) have the potential to be used as genetic markers to investigate host biodiversity and biogeographical patterns[1,2,3]
Most studies have focused on the use of the mitochondrial Cytochrome Oxidase I (COI) and Cytochrome Oxidase II (COII) genes[23,37,38,39,40,41,42], one laboratory has attempted to resolve the genetic structure and origin considering some pseudogenes of the symbiont, P. carbekii, as genetic markers (e.g. ΔybgF)[3]
Perhaps the most intriguing outcome of this study, and of a similar one conducted by Otero-Bravo & Sabree[3] was the finding of a higher haplotype diversity in the host species, H. halys than in the symbiont
Summary
Especially primary or obligatory symbionts (p-symbionts) have the potential to be used as genetic markers to investigate host biodiversity and biogeographical patterns[1,2,3]. P-symbionts are transmitted vertically, from mother to offspring, and may accurately mirror the history of their insect hosts. This helps, in the case of invasive host species by shedding light on their invasion p athways[2,4]. The highly invasive brown marmorated stink bug Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), harbours the primary, vertically transmitted symbiont ‘Candidatus Pantoea carbekii’ (hereafter referred to as Pantoea carbekii)[10]. Halyomorpha halys is native to Southeast Asia but has recently invaded North America and Europe causing substantial damage to agricultural crops and creating nuisance to residents in rural and urban a reas[12,13,14]. The bacterial marker did not explicitly incorporate geographic information among populations probably due to the limited sampling, especially in Europe[3]
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