脚踏石模型stepping-stone model # 作者信息 熊荣川 明湖实验室 xiongrongchuan@126.com http://blog.sciencenet.cn/u/Bearjazz 理论出处 In natural populations, individuals often are distributed more or less discontinuously to form numerous colonies, and individuals may be exchanged between adjacent or nearby colonies. To analyze such a situation, one of us proposed a model which he termed “stepping stone model” of population structure (KIMUR 1953) 在自然种群中，个体往往分布不连续，从而形成或多或少的聚居点，相邻或邻近的聚居点之间有一定的个体交流。为了分析这种情况，我们提出了一个模型，称这种种群结构为“脚踏石模型” (KIMUR 1953) 。 ONE DIMENSIONAL CASE Let US consider an infinite array of colonies with their position represented by integers on a line (Figure 1). The simplest situation for this one dimensional stepping stone model is that in each generation an individual can migrate at most one step” in either direction between colonies. In other words, exchange of individuals is restricted to be between adjacent colonies. 一维脚踏石模型 让我们考虑一个有无限多个聚居点的阵列，他们的位置用线上的整数表示（图 1 ）。这个一维的脚踏石模型的最简单的情况是，在聚居点之间，每一代个体最多可以在两个方向上迁移一步。换言之，个体交流被限制在相邻的聚居点之间。 Kimura, M. (1953). Stepping Stone model of population. Rep. Nat. Inst. Genetics Japan . 3: 62-63. Kimura, M. and G. H. Weiss (1964). The Stepping Stone Model of Population Structure and the Decrease of Genetic Correlation with Distance. Genetics 49 (4): 561-576.
大陆与岛屿植物遗传多样性进化 熊荣川 译 岛屿在植物进化生物学方面被赋予了极大的研究兴趣，因为它们面积有限以及和邻近大陆不同程度的隔离。大陆岛分布在大陆架上，其与大陆的隔离主要是海平面的抬升或是板块构造运动。因为海平面的变动，这些岛屿可能最近还和大陆通过大陆桥相连。相反，海岛则是由于火山喷发而从海底升起的岛屿，因此海岛上没有大陆生命的起源。因为海岛和大陆显著的时间和空间隔离，使得它们成为研究进化的较仿真实验室，成为研究植物历史迁移扩散及进化模式的理想系统。海岛上的物种形成及其具有不同的进化模式已有深入的研究，而很有少有研究关注同时在大陆和海岛分布的同一物种的种群分布，而这样的研究却能为理解决定物种早期分化和最近扩散的种内进化提供重要的线索。通常的观点认为岛屿上的种群遗传多样性低于大陆种群，因为其有限的基因流以及历史上可能存在的瓶颈效应。岛屿种群遗传多样性的衰退可能会损害其进化潜能甚至会导致其最终灭绝。进来对比大陆和岛屿种群的研究多选择大陆岛。这些研究案例的结果多支持大陆种群的遗传多样更高的观点。而发现大陆岛种群遗传多样性更高的研究结果可能是因为大陆岛多次从大陆引进种群；可能是因为大陆自己的遗传瓶颈效应；还有可能是物种最初发源地在大陆岛上，而后向大陆方向扩散。 ( Fernández-Mazuecos et al., 2011 ) 关键词：大陆岛 大陆 海岛 种群 遗传多样性 瓶颈效应 扩散 原文： Islands constitute a focus of research interest in plant evolutionary biology, given their limited area and varying degrees of isolation from nearby continents. Continental islands are located on continental shelves, and were isolated from the continent by means of rising sea level or/and by tectonic processes. These islands may have been recurrently connected to the continent by land bridges due to fluctuating sea levels. On the contrary, oceanic islands arise from the ocean floor, are usually of volcanic origin and have virtually no terrestrial life in origin , . Because they furnish clear-cut spatial and temporal limits, oceanic islands are considered to be living laboratories for evolution. That is why oceanic islands provide ideal systems to investigate historical colonization and evolutionary patterns in plants . Speciation processes giving rise to endemic species and lineages on oceanic islands have been widely discussed, leading to alternative models of evolution , , , , , . Less attention has been paid to populations of species distributed both on continents and oceanic islands. Nonetheless, populations of the same species distributed in insular and mainland areas can provide key insights into microevolutionary processes underlying recent colonization and early stages of differentiation. As a general pattern, lower levels of genetic variation are expected in island populations as compared to mainland populations due to founder effects and restricted gene flow . This depauperation may bring about an increased propensity for extinction and compromised evolutionary potential in island populations. Early studies of genetic variation in mainland and island populations included only one study of oceanic islands , . More recent examples of island-mainland comparisons have been reported, most of which also focused on continental islands , , , , . These examples generally agree with the expectation of higher genetic variation in mainland populations. The finding of higher variation in continental islands has been attributed to multiple continent-to-island introductions, genetic bottlenecks in the continent, or island-to-continent colonization , , . To our knowledge, higher genetic variation has not been reported for oceanic islands, where particularly strong genetic bottlenecks are expected due to isolation and the prevalence of single introduction events . 参考文献 Genetically Depauperate in the Continent but Rich in Oceanic Islands--Cistus mon.pdf Fernández-Mazuecos Mario,Vargas Pablo (2011). "Genetically Depauperate in the Continent but Rich in Oceanic Islands: Cistus monspeliensis (Cistaceae) in the Canary Islands." PloS one 6 (2): e17172.
标签: 种群
