Data from: Tropical Drosophila pandora carry Wolbachia infections causing cytoplasmic incompatibility or male killing

Wolbachia infections have been described in several Drosophila species, but relatively few have been assessed for phenotypic effects. Cytoplasmic incompatibility (CI) is the most common phenotypic effect that has been detected, while some infections cause male killing or feminization, and many Wolbachia infections have few host effects. Here, we describe two new infections in a recently described species, Drosophila pandora, one of which causes near-complete CI and near-perfect maternal transmission (the “CI” strain). The other infection is a male killer (the “MK” strain), which we confirm by observing reinitiation of male production following tetracycline treatment. No incompatibility was detected in crosses between CI strain males and MK strain females, and rare MK males do not cause CI. Molecular analyses indicate that the CI and MK infections are distantly related and the CI infection is closely related to the wRi infection of Drosophila simulans. Two population surveys indicate that all individuals are infected with Wolbachia, but the MK infection is uncommon. Given patterns of incompatibility among the strains, the infection dynamics is expected to be governed by the relative fitness of the females, suggesting that the CI infection should have a higher fitness. This was evidenced by changes in infection frequencies and sex ratios in population cages initiated at different starting frequencies of the infections.

已有多项研究在多种果蝇属（Drosophila）物种中检测到沃尔巴克氏体（Wolbachia）感染，但仅有相对较少的感染被系统评估了其表型效应。细胞质不相容（CI）是目前已发现的最常见表型效应；部分沃尔巴克氏体感染可引发雄性致死或雌性化现象，而多数感染仅对宿主产生微弱影响。本研究报道了在新定名物种潘多拉果蝇（Drosophila pandora）中发现的两株全新沃尔巴克氏体感染：其中一株可引发近乎完全的细胞质不相容，且具备近乎完美的母系传递能力，即“CI菌株”；另一株则为雄性致死菌株（“MK菌株”），我们通过四环素处理后观察到雄性繁殖能力恢复的现象，证实了这一表型。CI菌株雄虫与MK菌株雌虫的杂交实验未检测到不相容现象，且罕见的MK雄虫亦不会引发细胞质不相容。分子生物学分析结果显示，CI菌株与MK菌株的亲缘关系较远，而CI菌株与拟果蝇（Drosophila simulans）的wRi沃尔巴克氏体菌株亲缘关系密切。两项种群调查结果表明，该物种所有个体均携带沃尔巴克氏体感染，但MK菌株的感染率较低。结合各菌株间的不相容模式，推测感染动态主要由雌虫的相对适合度决定，这意味着CI菌株应具备更高的适合度。这一推论在以不同初始感染频率建立的种群笼实验中，通过感染频率与性比的变化得到了验证。