Kempf Florent, Boulinier Thierry, De Meeûs Thierry, Arnathau Céline, McCoy Karen D
Génétique et Evolution des Maladies Infectieuses, UMR CNRS-IRD 2724, IRD, BP 64501, 34394 Montpellier Cedex 5, France.
Mol Ecol. 2009 Nov;18(21):4450-62. doi: 10.1111/j.1365-294X.2009.04356.x. Epub 2009 Sep 29.
Ecological interactions are an important source of rapid evolutionary change and thus may generate a significant portion of novel biodiversity. Such changes may be particularly prevalent in parasites, where hosts can induce strong selection for adaptation. To understand the relative frequency at which host-associated divergences occur, it is essential to examine the evolutionary history of the divergence process, particularly when it is occurring over large geographical scales where both geographical and host-associated isolation may playa part. In this study, we use population genetics and phylogeography to study the evolutionary history of host-associated divergence in the seabird tick Ixodes uriae (Acari, Ixodidae). We compare results from microsatellite markers that reflect more ecological timescales with a conserved mitochondrial gene (COIII) that reflects more ancient divergence events. Population structure based on microsatellites showed clear evidence of host-associated divergence in all colonies examined. However, isolated populations of the same host type did not always group together in overall analyses and the genetic differentiation among sympatric host races was highly variable. In contrast, little host or geographical structure was found for the mitochondrial gene fragment. These results suggest that host race formation in I. uriae is a recent phenomenon, that it may have occurred several times and that local interactions are at different points in the divergence process. Rapid divergence in I. uriae implies a strong interaction with its local host species, an interaction that will alter the ecological dynamics of the system and modify the epidemiological landscape of circulating micropathogens.
生态相互作用是快速进化变化的重要来源，因此可能产生很大一部分新的生物多样性。这种变化在寄生虫中可能尤为普遍，因为宿主可以引发强烈的适应性选择。为了了解宿主相关分化发生的相对频率，研究分化过程的进化历史至关重要，特别是当这种分化发生在较大的地理尺度上时，地理隔离和宿主相关隔离都可能起作用。在本研究中，我们使用群体遗传学和系统地理学来研究海鸟蜱（硬蜱科，蜱属）中宿主相关分化的进化历史。我们将反映更多生态时间尺度的微卫星标记结果与反映更古老分化事件的保守线粒体基因（COIII）的结果进行比较。基于微卫星的群体结构在所有检测的群体中都显示出宿主相关分化的明显证据。然而，在总体分析中，相同宿主类型的隔离群体并不总是聚集在一起，同域宿主种族之间的遗传分化差异很大。相比之下，线粒体基因片段几乎没有发现宿主或地理结构。这些结果表明，海鸟蜱宿主种族的形成是一个近期现象，可能已经发生了几次，并且局部相互作用处于分化过程的不同阶段。海鸟蜱的快速分化意味着与其本地宿主物种有强烈的相互作用，这种相互作用将改变系统的生态动态，并改变传播的微病原体的流行病学格局。
