Development of genetic diversity, differentiation and structure over 500 years in four ponderosa pine populations

Population history plays an important role in shaping contemporary levels of genetic variation and geographic structure. This is especially true in small, isolated range-margin populations, where effects of inbreeding, genetic drift and gene flow may be more pronounced than in large continuous populations. Effects of landscape fragmentation and isolation distance may have implications for persistence of range-margin populations if they are demographic sinks. We studied four small, disjunct populations of ponderosa pine over a 500-year period. We coupled demographic data obtained through dendroecological methods with microsatellite data to discern how and when contemporary levels of allelic diversity, among and within-population levels of differentiation, and geographic structure, arose. Alleles accumulated rapidly following initial colonization, demonstrating proportionally high levels of gene flow into the populations. At population sizes of approximately 100 individuals, allele accumu...

种群历史对塑造当代遗传变异水平与地理格局具有关键作用。在小型、孤立的分布边缘种群中，这一作用尤为显著——近交、遗传漂变与基因流的效应较之于大型连续种群更为凸显。若分布边缘种群属于种群汇（demographic sink），景观破碎化与隔离距离所带来的效应可能会对其存续产生影响。本研究针对黄松（ponderosa pine）的4个小型间断种群展开了为期500年的调查。我们将通过树木年代生态学（dendroecological）方法获取的种群统计数据，与微卫星（microsatellite）数据相结合，以厘清当代等位基因多样性（allelic diversity）水平、种群间与种群内的分化水平，以及地理格局的形成路径与时间节点。初始定植后，等位基因快速积累，显示迁入这些种群的基因流比例处于较高水平。在种群规模约达100个个体时，等位基因积累...