Population Biology of Cytoplasmic Incompatibility in Drosophila simulans

在拟果蝇中，当受感染的雄性与未受感染的雌性交配时，一种垂直传播的细胞质不相容因子导致卵子孵化减少。这种不相容似乎与一种在加利福尼亚迅速传播的细胞内寄生虫（沃尔巴克氏体）有关。在建议资助年度的研究目标是通过以下方式进一步了解该系统的种群生物学：1)继续监测感染在加州的传播及其对线粒体DNA （mtDNA）变异分布的影响；2)确定是否可以通过后代检测确定沃尔巴克氏体的存在；3)获得多态自然种群的不亲和性水平和有害适合度效应的附加估计；4)利用现场和实验室数据构建描述现场时空频率动态的数学模型。新的数据和分析对于描述和了解感染的传播速度以及评估当前模型的充分性至关重要。该系统为研究自然种群的快速变化提供了难得的机会。在加利福尼亚迅速向北传播提供了许多重复的种群，其中发生了类似的频率变化。一个中心问题是描述一个区域动态的选择和迁移参数值是否能准确地预测其他区域的动态。感染和mtDNA变异的联合动力学为将细胞质遗传变异引入自然种群提供了一个模型系统。这种变种在控制害虫方面可能是有用的。鉴于只建议减少一年的经费，方案方案将集中于提供1992- 1993年秋、春、夏期间感染频率的详细地图。一个主要目标将是建立一种标准化的分子分析方法，以确定野外捕获的单个苍蝇是否受到感染，并确定感染原的存在与后代试验所揭示的不亲和性之间的表型关联。在时间和资金允许的范围内，pi还计划继续监测随感染“搭便车”的（mtDNA）变异的频率，并在不同地点和不同季节获得由感染引起的不相容性水平和生育力下降的额外现场估计。

In Drosophila simulans, a vertically transmitted, cytoplasmic incompatibility factor causes reduced egg hatch when infected males mate with uninfected females. The incompatibility seems to be associated with an intracellular parasite (Wolbachia) that is spreading rapidly in California. The goal of the research during the year of recommended funding is to understand further the population biology of this system by: 1) continuing to monitor the spread of the infection in California and its effect on the distribution of mitochondrial DNA (mtDNA) variants; 2) determining whether the presence of Wolbachia can be assertained by progeny tests; 3) obtaining additional estimates of incompatibility levels and deleterious fitness effects in polymorphic natural populations; and 4) using field and laboratory data to construct mathematical models describing temporal and spatial frequency dynamics in the field. The new data and analyses are essential for describing and understanding the rate of spread of the infection and assessing the adequacy of current models. This system offers an unusual opportunity to study rapid changes in natural populations. The rapid northward spread in California provides many replicate populations in which similar frequency changes are occurring. A central issue is whether the selection and migration parameter values that describe the dynamics in one area will accurately predict the dynamics elsewhere. The joint dynamics of the infections and mtDNA variants provide a model system for the introduction of cytoplasmically inherited variants into natural populations. Such variants may be useful in controlling insect pests. Given the reduced funding recommended for one year only, the PIs will concentrate on providing detailed maps of the infection frequency during the fall, spring and summer of 1992-93. A major goal will be to have a standardized molecular assay for determining whether individual field caught flies are infected, and to determine the phenotypic association between the presence of the infectious agent and incompatibility as revealed by progeny tests. To the extent that time and money permit, the PIs also plan to continue monitoring the frequency of (mtDNA) variants that are "hitch-hiking" along with the infection, and to obtain additional field estimates at different sites and in different seasons of the incompatibility levels and reductions of fecundity caused by the infection.