Sewell Mitchell M, Parks Clifford R, Chase Mark W
Department of Biology, University of North Carolina, Chapel Hill, North Carolina, 27599-3280.
Evolution. 1996 Jun;50(3):1147-1154. doi: 10.1111/j.1558-5646.1996.tb02355.x.
Restriction site variation in chloroplast DNA (cpDNA) was surveyed to analyze population dynamics in Liriodendron tulipifera L., a woody angiosperm found in eastern North America. Two cpDNA haplotypes, differing by the presence or absence of five restriction site changes (nucleotide sequence divergence estimated as approximately 0.15%) are geographically structured; 61 widespread populations possess the "northern" haplotype and three isolated populations of central Florida possess the "southern" haplotype. This geographic break in cpDNA distribution corresponds to patterns of geographic distribution revealed by a previous survey of allozyme variation, with the exception that analyses of allozyme data further divided the populations containing the northern cpDNA haplotype into two groups, a widespread upland group and a coastal intermediate group. Analyses of these two independent data sets together support the hypothesis that L. tulipifera survived the glacial advances of the Pleistocene in two distinct refugia, possibly as different taxa, and the intermediate coastal group was putatively formed from recent hybridizations between these entities.
对北美东部木本被子植物北美鹅掌楸叶绿体DNA（cpDNA）的限制性位点变异进行了调查，以分析其种群动态。两种cpDNA单倍型在地理上呈现出结构差异，它们因五个限制性位点变化的有无而不同（核苷酸序列差异估计约为0.15%）；61个分布广泛的种群具有“北方”单倍型，而佛罗里达州中部的三个孤立种群具有“南方”单倍型。cpDNA分布的这种地理间断与先前对等位酶变异调查所揭示的地理分布模式相对应，不同之处在于，对等位酶数据的分析进一步将包含北方cpDNA单倍型的种群分为两组，一组是分布广泛的高地种群，另一组是沿海中间种群。对这两个独立数据集的分析共同支持了这样一种假设，即北美鹅掌楸在更新世的冰川推进过程中在两个不同的避难所中存活下来，可能作为不同的分类群，而中间的沿海种群推测是由这些实体之间最近的杂交形成的。
