Genetic diversity as to endemic, relict plants

采用酶电泳法对濒危树种白蜡梅的遗传变异进行了研究。本种在日本仅分布在两个限制区域：对马岛的最北端和本州中部的东部岐阜县(东野区)。在托诺地区，在人类活动的影响下，白背飞虱的栖息地正在变得支离破碎，每一林分都有几只白背飞虱，而对马岛上的种群大约有1000只。从化石演化来看，包括这两个地区在内的两个地区一直在分布，目前的分布显然是日本的遗迹。与Tono种群相比，对马的种群似乎是稳定的。比较这两个地区的种群的遗传多样性和分化，将有助于了解木本长寿植物如何保持和/或丧失其遗传多样性，以及种群如何与其他分离的种群区分开来。Tono区18个基因座的等位酶电泳显示，22.2%的座位是多态的(P)，基因多样性为(H)0.087。对马种群具有38.9%的多态位点数和0.149的基因多样性。通过空间自相关分析，在托诺地区找不到红曲柳的空间遗传结构。这些结果表明，托诺地区仍然存在相当大的遗传变异，最近栖息地碎片化的影响似乎还不是很大。由于红曲柳是一种长寿树，种群历史可能会阻碍目前碎片化的效果，东野和对马种群间的遗传多样性为0.280，表明这两个地区之间已经发生了遗传分化。

Genetic variation in an endangered tree species, Chionanthus retusus, was examined using enzyme electrophoresis. This species occurs in Japan only in two restricted areas : at the northernmost tip of Tsushima Island, and in the eastern Gifu Prefecture (Tono region) of central Honshu. In the Tono region, the habitat of C.retusus is becoming fragmented under the influence of human activity and each stand contains a few individuals of C.retusus, while the population on Tsushima consists of approximately 1000 individuals. From the fossil evedence, C.retusus has been distrubuted continuously including the both two regions, and the present distribution is apparently relic in Japan. In contrast to the Tono population, the population of Tsushima seems to be stable. Comparing the genetic diversity and differentiation of the populations between these two regions should shed light on how a relic woody long-lived plant keeps and/or looses its genetic diversity, and how a population differentiates from other disjunct populations.Allozyme electrophoresis of 18 loci for the Tono region indicated that 22.2% of the loci are polymorphic (P) with a gene diversity of (h) 0.087. The population of Tsushima has 38.9% polymorphic loci and gene diversity of 0.149. We could not find any spatial genetic structure of C.retusus in the Tono region by spatial autocorrelation analysis. These results suggest that considerable genetic variation is still present in the Tono region and the influence of the recent habitat fragmentation seems not so large, yet. Because C.retusus is a long-livied tree, the population history may hinder the effect of the fragmentation at present.The genetic diversity (GST) between the populations of the Tono and Tsushima is 0.280, showing the genetic differentiation between these two regions has occurred.