Center for Population Biology and Department of Evolution and Ecology, University of California, One Shields Avenue, Davis, California 95616, USA.
Evolution. 2011 Apr;65(4):1011-20. doi: 10.1111/j.1558-5646.2010.01183.x. Epub 2010 Dec 3.
Understanding how genetic variation shapes species' distributions involves examining how variation is distributed across a species' range as well as how it responds to underlying environmental heterogeneity. We examined patterns of fitness variation across the local distribution of an annual composite (Lasthenia fremontii) spanning a small-scale inundation gradient in a California vernal pool wetland. Using seeds collected from the center and edge of a population, paternal half-sib families were generated and transplanted back to the center and edge of the original population. All transplants were adapted to the conditions at the center of the population. The effect of the environment on the opportunity for selection depended on the model of selection assumed. Under a model of hard selection, variance in absolute fitness was lower among transplants at the edge of the population than at the center. Under a model of soft selection, the variance in relative fitness was similar between center and edge microhabitats. Given that this population is likely well-mixed, differences in habitat quality between center and edge microhabitats will likely cause selection at the center of the population to dominate the evolutionary trajectory of this population.
理解遗传变异如何塑造物种的分布范围，需要研究变异在物种分布范围内是如何分布的，以及它如何对潜在的环境异质性做出响应。我们研究了在加利福尼亚州春池湿地一个小规模泛滥梯度范围内分布的一年生复合种（Lasthenia fremontii）的适应性变化模式。从种群中心和边缘采集种子，生成父系半同胞家系，并将其移植回原始种群的中心和边缘。所有的移植都适应了种群中心的条件。环境对选择机会的影响取决于所假设的选择模型。在硬选择模型下，种群边缘的移植体的绝对适应性方差低于种群中心。在软选择模型下，中心和边缘微生境之间的相对适应性方差相似。鉴于该种群很可能是混合的，中心和边缘微生境之间的栖息地质量差异可能会导致种群中心的选择主导该种群的进化轨迹。
