Schebeck Martin, Feldkirchner Lukas, Marín Belen, Krumböck Susanne, Schuler Hannes, Stauffer Christian
Department of Forest and Soil Sciences, University of Natural Resources and Life Sciences, BOKU, Peter-Jordan-Straße, Vienna, Austria.
J Insect Sci. 2018 May 1;18(3). doi: 10.1093/jisesa/iey044.
Heritable bacterial endosymbionts can alter the biology of numerous arthropods. They can influence the reproductive outcome of infected hosts, thus affecting the ecology and evolution of various arthropod species. The spruce bark beetle Pityogenes chalcographus (L.) (Coleoptera: Curculionidae: Scolytinae) was reported to express partial, unidirectional crossing incompatibilities among certain European populations. Knowledge on the background of these findings is lacking; however, bacterial endosymbionts have been assumed to manipulate the reproduction of this beetle. Previous work reported low-density and low-frequency Wolbachia infections of P. chalcographus but found it unlikely that this infection results in reproductive alterations. The aim of this study was to test the hypothesis of an endosymbiont-driven incompatibility, other than Wolbachia, reflected by an infection pattern on a wide geographic scale. We performed a polymerase chain reaction (PCR) screening of 226 individuals from 18 European populations for the presence of the endosymbionts Cardinium, Rickettsia, and Spiroplasma, and additionally screened these individuals for Wolbachia. Positive PCR products were sequenced to characterize these bacteria. Our study shows a low prevalence of these four endosymbionts in P. chalcographus. We detected a yet undescribed Spiroplasma strain in a single individual from Greece. This is the first time that this endosymbiont has been found in a bark beetle. Further, Wolbachia was detected in three beetles from two Scandinavian populations and two new Wolbachia strains were described. None of the individuals analyzed were infected with Cardinium and Rickettsia. The low prevalence of bacteria found here does not support the hypothesis of an endosymbiont-driven reproductive incompatibility in P. chalcographus.
可遗传的细菌内共生体能够改变众多节肢动物的生物学特性。它们会影响受感染宿主的繁殖结果，进而影响各种节肢动物物种的生态和进化。据报道，云杉小蠹（Pityogenes chalcographus (L.)，鞘翅目：象甲科：小蠹亚科）在某些欧洲种群中表现出部分单向杂交不亲和性。然而，目前尚缺乏对这些研究结果背景的了解；不过，人们推测细菌内共生体可能操控了这种小蠹的繁殖。此前的研究报告称，云杉小蠹感染沃尔巴克氏体的密度较低且频率不高，但发现这种感染不太可能导致繁殖改变。本研究的目的是检验除沃尔巴克氏体外，由内共生体驱动的不亲和性这一假说，该假说通过广泛地理尺度上的感染模式得以体现。我们对来自18个欧洲种群的226个个体进行了聚合酶链反应（PCR）筛查，以检测内共生体卡丁氏菌（Cardinium）、立克次氏体（Rickettsia）和螺原体（Spiroplasma）的存在情况，并额外对这些个体进行了沃尔巴克氏体的筛查。对PCR阳性产物进行测序以鉴定这些细菌。我们的研究表明，这四种内共生体在云杉小蠹中的感染率较低。我们在来自希腊的一个个体中检测到一种尚未描述的螺原体菌株。这是首次在小蠹中发现这种内共生体。此外，在来自两个斯堪的纳维亚种群的三只小蠹中检测到了沃尔巴克氏体，并描述了两种新的沃尔巴克氏体菌株。所分析的个体均未感染卡丁氏菌和立克次氏体。此处发现的细菌低感染率并不支持内共生体驱动云杉小蠹繁殖不亲和性这一假说。
