CCMAR, CIMAR-Laboratório Associado, Universidade do Algarve Gambelas, 8005-139 Faro, Portugal.
Oecologia. 2011 Apr;165(4):947-58. doi: 10.1007/s00442-010-1788-9. Epub 2010 Sep 29.
Understanding patterns of gene flow, selection and genetic diversity within and among populations is a critical element of predicting how long-term changes in environmental conditions are likely to affect species distribution. The intertidal mussel Perna perna consists of two distinct genetic lineages in South Africa, but the mechanisms maintaining these lineages remains obscure. We used regional oceanography and lineage-specific responses to environmental conditions as proxies for gene flow and local selection, respectively, to test how these mechanisms could shape population genetic structure. Laboratory experiments supported the field findings that mussels on the east coast (eastern lineage) are physiologically more tolerant of sand inundation and high temperatures than those on the south coast (western lineage). Temperature loggers mimicking mussel body temperatures revealed that mussels experience higher body temperatures during aerial exposure on the subtropical east coast than on the temperate south coast. Translocations showed that, on the east coast, the western lineage suffered higher mortality rates than local individuals, while on the south coast, mortality rates did not differ significantly between the lineages. Nearshore drogues showed remarkably little overlap between the trajectories of drifters released off the south coast and those released off the east coast. Physiological tolerances can thus explain the exclusion of western individuals from the east coast, but they cannot explain the exclusion of the eastern lineage from the south coast. In contrast, however, ocean dynamics may limit larval dispersal between the two lineages, helping to explain the absence of eastern individuals from the south coast. We emphasise the importance of a multidisciplinary approach in a macro-ecological context to understand fully the mechanisms promoting evolutionary divergence between genetic entities. Our results suggest that phylogeographic patterns of Perna perna may be maintained by a combination of local conditions and the isolating effect of the Agulhas Current that reduces gene exchange.
了解基因流、选择和遗传多样性在种群内和种群间的模式是预测长期环境变化如何影响物种分布的关键因素。南非的贻贝 Perna perna 由两个截然不同的遗传谱系组成，但维持这些谱系的机制尚不清楚。我们分别使用区域海洋学和谱系特异性对环境条件的反应作为基因流和局部选择的替代指标，以检验这些机制如何塑造种群遗传结构。实验室实验支持了野外研究的结果，即东海岸的贻贝（东部谱系）在生理上比南海岸的贻贝（西部谱系）更能耐受泥沙淤积和高温。模拟贻贝体温的温度记录仪显示，在亚热带东海岸暴露于空气中时，贻贝的体温比在温带南海岸更高。移植实验表明，在东海岸，西部谱系的死亡率高于当地个体，而在南海岸，两个谱系的死亡率没有显著差异。近岸浮标显示，从南海岸释放的漂移器轨迹与从东海岸释放的漂移器轨迹之间几乎没有重叠。因此，生理耐受性可以解释为什么西部个体被排除在东海岸之外，但不能解释为什么东部谱系被排除在南海岸之外。相比之下，然而，海洋动力学可能限制了两个谱系之间的幼虫扩散，有助于解释为什么东海岸没有东部个体。我们强调在宏观生态背景下采用多学科方法的重要性，以充分了解促进遗传实体之间进化分歧的机制。我们的结果表明，贻贝 Perna perna 的系统地理格局可能是由局部条件和隔离阿古拉斯洋流的影响共同维持的，这种洋流减少了基因交换。
