Les Donald H, Reinartz James A, Esselman Elizabeth J
Department of Biological Sciences, P.O. Box 413.
The University of Wisconsin-Milwaukee, Milwaukee, WI, 53201, USA.
Evolution. 1991 Nov;45(7):1641-1650. doi: 10.1111/j.1558-5646.1991.tb02669.x.
Aster furcatus is a rare, self-incompatible plant with fewer than 50 known populations throughout its range. We verified self-incompatibility in A. furcatus by conducting experimental self- and cross-pollinations and by examining seed set in a small population comprised of a single clonal genet. We examined variation at 22 electrophoretic loci in 23 populations of A. furcatus from across its range in Wisconsin, Illinois, Indiana, and Missouri. Except for two rare alleles found in single individuals in three populations, all loci but one of those examined were fixed for single alleles. The only variable locus (triosephosphate isomerase, TPI-1) tended to exhibit genotype frequencies in Hardy-Weinberg equilibrium or with a slight excess of heterozygotes. Although overall gene diversity was extremely low, TPI genotype frequencies were indicative of an outcrossing plant. We examined the subpopulation genetic structure among clonal plants within one Wisconsin population in greater detail. F statistics indicated that much of the genetic variation at the polymorphic TPI locus was due to differentiation among populations. We discuss the implications of self-incompatibility and low levels of genetic variation for the evolution and conservation of Aster furcatus and other rare plants with similar breeding systems.
叉枝紫菀是一种稀有的自交不亲和植物，在其整个分布范围内已知种群少于50个。我们通过进行实验性的自花授粉和异花授粉，并通过检查由单个克隆基株组成的小种群中的结实情况，验证了叉枝紫菀的自交不亲和性。我们研究了来自威斯康星州、伊利诺伊州、印第安纳州和密苏里州叉枝紫菀23个种群中22个电泳位点的变异情况。除了在三个种群的单个个体中发现的两个稀有等位基因外，所检测的位点中除一个外其余均固定为单个等位基因。唯一的可变位点（磷酸丙糖异构酶，TPI-1）的基因型频率倾向于呈现哈迪-温伯格平衡，或杂合子略有过量。尽管总体基因多样性极低，但TPI基因型频率表明这是一种异交植物。我们更详细地研究了威斯康星州一个种群内克隆植物的亚种群遗传结构。F统计量表明，多态性TPI位点的大部分遗传变异是由于种群间的分化所致。我们讨论了自交不亲和性和低水平遗传变异对叉枝紫菀以及其他具有类似繁育系统的稀有植物的进化和保护的影响。
