Richards Christopher M, Church Sheri, McCauley David E
Department of Botany, Duke University, Durham, North Carolina, 27708.
Department of Biology, Vanderbilt University, Nashville, Tennessee, 37235.
Evolution. 1999 Feb;53(1):63-73. doi: 10.1111/j.1558-5646.1999.tb05333.x.
In a series of experiments conducted over two seasons, we used arrays of experimental populations to examine the effects of flower number and distance between patches on gene flow by pollen. For this study we used the dioecious, short-lived perennial plant Silene alba (Caryophyllaceae). This species lives in disturbed roadside and agricultural habitats and displays a weedy population dynamic with high colonization and extinction rates. The motivation for the study was to understand what factors may be influencing genetic connectedness among newly colonized populations within a regional metapopulation. By using experimental populations composed of genotypes homozygous at a diagnostic locus, it was possible to identify explicitly pollen movement into a focal patch as a function of flower number and distance to the nearest neighboring patch. Overall, the mean immigration rate (measured as the fraction of seeds sired by males outside the focal patch) at 20 m was just over 47%, whereas at 80 m immigration rates were less than 6%. In addition, by knowing the context in which each of these gene-flow events occurred, it was possible to understand some of the factors that influenced the exchange of genes. Both the number of flowers in the focal population (target) and in the neighboring populations (source) had a significant effect on the frequency of gene flow. Our experimental data also demonstrate that factors that influence gene flow at one spatial scale may not act in the same way at another. Specifically, the influence of target size and the relative size of the target and source patches on rates of gene flow depended on whether the patches were separated by 20 m or 80 m. These data suggest that the patterns of gene flow within a metapopulation system can be complex and may vary within a growing season.
在跨越两个季节进行的一系列实验中，我们使用实验种群阵列来研究花的数量和斑块间距离对花粉介导的基因流动的影响。在本研究中，我们使用了雌雄异株的一年生短命植物白麦瓶草（石竹科）。该物种生活在受干扰的路边和农业生境中，呈现出具有高定殖率和灭绝率的杂草种群动态。本研究的目的是了解哪些因素可能影响区域集合种群中新定殖种群之间的遗传连通性。通过使用由在一个诊断位点纯合的基因型组成的实验种群，能够明确地将进入目标斑块的花粉移动确定为花的数量和到最近邻斑块距离的函数。总体而言，在20米处的平均迁入率（以目标斑块外雄性产生的种子比例衡量）略高于47%，而在80米处迁入率低于6%。此外，通过了解这些基因流动事件中每一个发生的背景，就有可能理解一些影响基因交换的因素。目标种群（靶标）和邻近种群（源）中的花的数量都对基因流动频率有显著影响。我们的实验数据还表明，在一个空间尺度上影响基因流动的因素在另一个尺度上可能不会以相同方式起作用。具体而言，目标大小以及目标和源斑块的相对大小对基因流动速率的影响取决于斑块是被20米还是80米隔开。这些数据表明，集合种群系统内的基因流动模式可能很复杂，并且在一个生长季节内可能会有所不同。
