Data from: 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 accumulation saturated. Levels of genetic differentiation among populations (FST and Jost's Dest) and diversity within populations (FIS) remained stable through time. There was no evidence of geographic genetic structure at any time in the populations' history. Proportionally, high gene flow in the early stages of population growth resulted in rapid accumulation of alleles and quickly created relatively homogenous genetic patterns among populations. Our study demonstrates that contemporary levels of genetic diversity were formed quickly and early in population development. How contemporary genetic diversity accumulates over time is a key facet of understanding population growth and development. This is especially relevant given the extent and speed at which species ranges are predicted to shift in the coming century.种群历史对于塑造当代遗传变异水平与地理遗传结构具有重要意义。对于小型隔离的分布边缘种群而言尤为如此——近交、遗传漂变与基因流的效应相较于大型连续分布种群更为显著。若分布边缘种群属于种群汇，则景观破碎化与隔离距离的效应可能会对其存续产生影响。本研究以500年为时间尺度，对4个小型间断分布的美国黄松（Ponderosa pine）种群展开研究。我们将通过树轮生态学方法获取的种群统计数据与微卫星数据相结合，以解析当代等位基因多样性水平、种群间及种群内的遗传分化水平与地理遗传结构的形成方式与时间节点。等位基因在初始定殖后快速积累，表明迁入种群的基因流比例较高。当种群规模约为100个个体时，等位基因积累达到饱和。种群间遗传分化水平（FST与Jost's Dest）及种群内遗传多样性（FIS）随时间保持稳定。在种群历史的任一时期均未检测到地理遗传结构的存在。种群增长早期的高比例基因流推动了等位基因的快速积累，并迅速在种群间形成了相对均一的遗传模式。本研究表明，当代遗传多样性水平在种群发展的早期便快速形成。解析当代遗传多样性随时间的积累方式，是理解种群增长与发展的核心维度之一。考虑到本世纪内物种分布范围预计将发生的变化幅度与速度，这一点尤为重要。