Brandt Miriam, Fischer-Blass Birgit, Heinze Jürgen, Foitzik Susanne
Department Biology I, University Regensburg, 93040 Regensburg, Germany.
Mol Ecol. 2007 May;16(10):2063-78. doi: 10.1111/j.1365-294X.2007.03300.x.
Co-evolutionary trajectories of host-parasite interactions are strongly affected by the antagonists' evolutionary potential, which in turn depends on population sizes as well as levels of recombination, mutation, and gene flow. Under similar selection pressures, the opponent with the higher evolutionary rate is expected to lead the co-evolutionary arms race and to develop local adaptations. Here, we use mitochondrial DNA sequence data and microsatellite markers to assess the amount of genetic variability and levels of gene flow in two host-parasite systems, each consisting of an ant social parasite--the European slavemaker Harpagoxenus sublaevis and the North American slavemaker Protomognathus americanus--and its two main host species. Our population genetic analyses revealed limited gene flow between individual populations of both host and parasite species, allowing for a geographic mosaic of co-evolution. In a between-system comparison, we found less genetic variability and more pronounced structure in Europe, where previous behavioural studies demonstrated strong local adaptation. Within the European host-parasite system, the larger host species Leptothorax acervorum exhibited higher levels of both genetic variability and gene flow, and previous field data showed that it is less affected by the social parasite H. sublaevis than the smaller host Leptothorax muscorum, which has genetically depleted and isolated populations. In North America, the parasite P. americanus showed higher levels of gene flow between sites, but overall less genetic diversity than its hyper-variable main host species, Temnothorax longispinosus. Interestingly, recent ecological and chemical studies demonstrated adaptation of P. americanus to local host populations, indicating the importance of migration in co-evolutionary interactions.
宿主 - 寄生虫相互作用的共同进化轨迹受到拮抗者进化潜力的强烈影响，而进化潜力又取决于种群大小以及重组、突变和基因流的水平。在相似的选择压力下，进化速率较高的一方有望主导共同进化的军备竞赛并形成局部适应性。在此，我们使用线粒体DNA序列数据和微卫星标记来评估两个宿主 - 寄生虫系统中的遗传变异性数量和基因流水平，每个系统都由一种蚂蚁社会性寄生虫——欧洲奴役蚁Harpagoxenus sublaevis和北美奴役蚁Protomognathus americanus——及其两种主要宿主物种组成。我们的群体遗传学分析揭示了宿主和寄生虫物种的各个种群之间的基因流有限，从而形成了共同进化的地理镶嵌模式。在系统间比较中，我们发现欧洲的遗传变异性较低且结构更为明显，此前的行为学研究表明欧洲存在强烈的局部适应性。在欧洲宿主 - 寄生虫系统中，体型较大的宿主物种聚群细胸蚁Leptothorax acervorum表现出更高的遗传变异性和基因流水平，并且此前的野外数据表明，与体型较小的宿主藓生细胸蚁Leptothorax muscorum相比，它受社会性寄生虫H. sublaevis的影响较小，藓生细胸蚁的种群在遗传上已经枯竭且相互隔离。在北美，寄生虫P. americanus在不同地点之间表现出较高的基因流水平，但总体遗传多样性低于其高度可变的主要宿主物种长棘细胸蚁Temnothorax longispinosus。有趣的是，最近的生态学和化学研究表明P. americanus对当地宿主种群具有适应性，这表明迁移在共同进化相互作用中的重要性。
