Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, S-901 83, Umeå, Sweden.
Theor Appl Genet. 1996 Mar;92(3-4):436-41. doi: 10.1007/BF00223690.
We studied allozyme and chloroplast (cp) DNA variation in natural populations of Pinus kesiya and P. merkusii from Thailand and Vietnam. The results showed striking differences between the two species in the amount and distribution of allozyme variation. P. kesiya harboured considerable allozyme variation and showed weak interpopulational differentiation. In contrast, P. merkmii had very low intrapopulational variability but a high level of interpopulational differentiation. The average Nei's genetic distance separating the two species was exceptionally high (0.701) taking into account their close taxonomic placement in the same subsection Sylvestres. The constructed phylogenetic trees revealed very early divergence of P. kesiya and P. merkusii. The present analysis of cpDNA variation also confirmed the dissimilar character of these two species and was compatible with other evidence indicating the outstanding position of P. merkusii as compared to other Asian members of the subsection Sylvestres. Analysis of cpDNA variation in sympatric populations of P. kesiya and P. merkusii revealed that they are pure representatives of the species in question. This result indicates that despite an overlapping distribution P. kesiya and P. merkusii do not hybridise in nature. We suggest that the distinctive character of P. merkusii is a result of an early separation from other Eurasian pines. Despite spatial proximity, P. kesiya and P. merkusii are kept apart by strong reproductive barriers. The low genetic variability of P. merkusii may be explained by previous bottlenecks, reduced gene flow among populations, and an inbreeding due to small population size and asynchronous flowering.
我们研究了来自泰国和越南的天然群体中的松科柏木和松科松属的同工酶和叶绿体 (cp) DNA 变异。结果表明，这两个物种在同工酶变异的数量和分布上存在显著差异。松科柏木具有相当大的同工酶变异，表现出较弱的种群间分化。相比之下，松科松属的种群内变异性非常低，但种群间分化程度很高。考虑到它们在同一亚科 Sylvestres 中的密切分类位置，两个物种之间的平均 Nei 遗传距离非常高 (0.701)。构建的系统发育树揭示了松科柏木和松科松属的早期分化。对 cpDNA 变异的分析也证实了这两个物种的不同特征，与其他表明松科松属与其他亚洲 Sylvestres 成员相比具有突出地位的证据一致。对松科柏木和松科松属同域种群的 cpDNA 变异分析表明，它们是所讨论物种的纯代表。这一结果表明，尽管分布重叠，但松科柏木和松科松属在自然界中不会杂交。我们认为，松科松属的独特特征是其与其他欧亚松属早期分离的结果。尽管空间上接近，但松科柏木和松科松属通过强大的生殖障碍而分开。松科松属的遗传变异性低可能是由于先前的瓶颈、种群间基因流减少以及由于种群规模小和开花不同步导致的近交所致。
