Landscape structure and hierarchical genetic diversity in the brook charr, Salvelinus fontinalis
Landscape structure and hierarchical genetic diversity in the brook charr, Salvelinus fontinalis
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DOI：
10.1554/0014-3820(2001)055
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发表时间：
2001-05-01
期刊：
影响因子：
3.3
通讯作者：
Bernatchez, L
中科院分区：
文献类型：
--
作者：
Castric, V;Bonney, F;Bernatchez, L
解释生物在空间中分布的范围、原因和后果是我们理解物种如何进化和应对特定环境的基础。然而，识别景观结构对迁徙的外在障碍并预测其对种内遗传多样性的影响仍然是种群生物学中的一大挑战。本研究对来自美国缅因州的6个主要河流流域的30个种群(771只鲑科)的遗传多样性进行了6个微卫星座位的研究，以量化栖息地、海拔、当代和历史连通性等景观特征在三个空间尺度上对遗传多样性的影响：湖泊内、河流流域内和河流流域之间。种群内期望杂合度与海拔呈负相关，与湖泊大小无显著相关。相反，湖泊内杂合子缺乏的程度与栖息地大小呈负相关。遗传方差的层次分析表明，相对于流域内明显的群体结构，流域间的分化程度出乎意料地低。地理上邻近的圣约翰河和佩诺斯科特河流域的特点是海拔和地理距离在塑造流域内种群分化格局方面具有相反的影响。不同流域之间的地理分化模式既不能用距离隔离来解释，也不能用逐步范围扩大模型来解释。总体而言，这项研究为当代景观特征在较小地理尺度(在河流流域内的种群内和种群之间)形成所观察到的遗传多样性格局提供了证据。在更广泛的地理尺度上，当代景观结构似乎只是决定所观察到的流域间遗传结构模式的一个次要因素。这些结果增加了越来越多的证据表明，在广泛的动物分类群中，漂移和迁徙之间存在非平衡条件。因此，发展对非平衡种群结构的更现实的理论描述，对于更好地理解历史和生态因素在形成年轻栖息地(如最近冰川消融地区)遗传变异方面的相对影响似乎是重要的。
Explaining the extent, causes, and consequences of biotic distributions in space is fundamental to our understanding of how species evolve and cope with particular environments. Yet, identifying extrinsic barriers to migration imposed by landscape structure and predicting their impacts on intraspecific genetic diversity remains a major challenge in population biology. In this study, 30 populations (771 individuals) of brook charr (Salvelinus fontinalis, Salmonidae) representing six major river drainages from Maine, USA, were characterized at six microsatellite loci to quantify the role of landscape features, such as habitat site, altitude, contemporary and historical connectivity, in shaping genetic diversity at three spatial scales: within lakes, within river drainages, and among river drainages. Within-population expected heterozygosity was negatively correlated with altitude, whereas no significant correlation was observed with lake size. Conversely, the extent of heterozygote deficiency within lakes was negatively associated with habitat size. The hierarchical analysis of genetic variance revealed that the extent of among-drainage differentiation was unexpectedly low relative to the pronounced population structuring within drainage. Geographically proximate St. John and Penobscot River drainages were characterized by opposite effects of altitude and geographic distance in shaping the pattern of population differentiation within drainages. The geographic pattern of differentiation among drainages could not be accounted for either by an isolation by distance or by a stepwise range expansion model. Overall, this study provided evidence for the role of contemporary landscape features in shaping the observed pattern of genetic diversity at smaller geographic scales (within and among populations within river drainage). On a broader geographic scale, contemporary landscape structure appeared to be only a minor factor determining the observed pattern of genetic structuring among drainages. These results add to the increasing evidence for nonequilibrium conditions between drift and migration in a wide array of animal taxa. The development of more realistic theoretical descriptions of nonequilibrium population structure thus appears to be important to better understand the relative influence of historical and ecological factors in shaping genetic variation in young habitats, such as recently deglaciated areas.