摘要
杂交实验结果表明，石荠苎属（唇形科）中国产的７个种，即小花荠苎Ｍｏｓｌａｃａｖａｌｅｒｉｅｉ、石香薷Ｍ．ｃｈｉｎｅｎｓｉｓ、小鱼仙草Ｍ．ｄｉａｎｔｈｅｒａ、杭州石荠苎Ｍ．ｈａｎｇｃｈｏｕｅｎｓｉｓ、疏花荠苎Ｍ．ｐａｕｃｉｆｌｏｒａ、石荠苎Ｍ．ｓｃａｂｒａ和苏州石荠苎Ｍ．ｓｏｃｈｏｕｅｎｓｉｓ，彼此之间生殖隔离。这７个种中，疏花荠苎是四倍体，由杂交伴随多倍化产生。根据２１个代表居群在１５个酶系统的２８个位点的等位酶资料分析，其余６个二倍体种组成３个亲缘关系密切的种对。杭州石荠苎和石香薷的亲缘关系最近，石香薷可能由于涉及繁育系统类型的大突变而与杭州石荠苎分化开来。小花荠苎与小鱼仙草比较接近，但它们的遗传分化很显著，除了突变之外，染色体结构也有大的变异，最明显的表现是随体的位置不同，小花荠苎的随体位于长臂上，而小鱼仙草与其它种一样，随体位于短臂上。石荠苎和苏州石荠苎在酶基因位点上的分化不大，但生境隔离、花期隔离和繁育系统的差别等能有效地保持种的独立性。不同的生境要求、不同的花期、花的形态结构的分化、繁育系统类型的不同、杂种Ｆ１代高度不育、染色体数目和核型的差异等均为石荠苎属下种间有效的隔离机制，而且近缘种间常是多?
Seven species were recognized in Mosla in China. M. pauciflora (C. Y. Wu) C. Y. Wu et H. W. Li is an allotetraploid (2n=36), while the other six species are diploids (2n=18). Cluster analysis based on allozyme data from 28 loci of 15 enzyme systems reveals that the six diploid species formed three species pairs. M. cavaleriei Lévl. is closely related to M. dianthera (Buch. Ham. ex Roxb.) Maxim., M. chinensis and M.hangchouensis Matsuda are sibling species, and M. scabra (Thunb.) C. Y. Wu et H. W. Li is allied to M. soochouensis. Although M. cavaleriei and M. dianthera are close relatives, considerable genetic divergence has been detected between them. One third of alleles are unique to either of them, and 28.6% of their loci have different alleles fixed. The average genetic identity (I) between populations of these two species is 0.770, and the average genetic distance (D) is 0.261. M. scabra and M. soochouensis are the least divergent species pair (I=0.979, D=0.025). No completely divergent locus was detected, and the percentages of unique alleles are 11.1% to M. scabra and 16.7% to M. soochouensis. This finding indicates that a high level of genetic differentiation is unnecessarily a prerequisite of speciation. A moderate divergence is detected between M. chinensis and M. hangchouensis (I=0.899, D=0.107, and 7.1% of completely diverged loci) yet the latter harbors four times as many unique alleles (45.1%) as the former does( 11.8% ). Compared to the genetic divergence between M. scabra and M. soochouensis, M. dianthera and M. hangchouensis and may well been undergoing active speciation have the high genetic distance between populations (0.034 and 0.026 respectively).
出处
《植物分类学报》
CSCD
1999年第1期10-19,共10页
Acta Phytotaxonomica Sinica
基金
国家自然科学基金
中国科学院生物分类区系特别支持项目
