Sytsma Kenneth J, Schaal Barbara A
Biology Department, Washington University, St. Louis, MO, 63130.
Evolution. 1985 May;39(3):582-593. doi: 10.1111/j.1558-5646.1985.tb00396.x.
An isozyme investigation of the Lisianthius skinneri (Gentianaceae) species complex in central Panama assayed levels of genetic variation within and among isolated populations and was used to reconstruct phylogenetic relationships within the complex. The widespread and low elevation L. skinneri and one derived cloud forest endemic species, L. habuensis, are depauperate in genetic variation. Three other endemic cloud forest species exhibiting larger population sizes and apparently more outcrossed breeding systems have higher levels of heterozygosity but retain low levels of allelic diversity. More than 90% of the genetic variation in the species complex is confined to among-population differentiation rather than witnin-population variation. Isozyme-based relationships within the species complex using both genetic divergence values (Fitch and Margoliash algorithm) and shared allelic states (Nelson and Van Horn algorithm) are identical. This network is not entirely congruent with a previous DNA-based network. Geographical isolation, small population size, low allelic diversity, and high levels of among-population differentiation suggest that repeated instances of founder events and genetic drift have been important in the evolution of this tropical shrub complex.
对巴拿马中部的斯氏瓶儿小草（龙胆科）物种复合体进行的同工酶研究，测定了隔离种群内部和种群之间的遗传变异水平，并用于重建该复合体内部的系统发育关系。分布广泛且海拔较低的斯氏瓶儿小草以及一个衍生的云雾林特有物种哈氏瓶儿小草，遗传变异匮乏。另外三个云雾林特有物种种群规模较大，且显然具有更多异交繁殖系统，杂合度较高，但等位基因多样性水平较低。该物种复合体中超过90%的遗传变异局限于种群间分化而非种群内变异。使用遗传分歧值（菲奇和马戈利亚什算法）和共享等位基因状态（尼尔森和范霍恩算法）得出的基于同工酶的物种复合体内关系是一致的。这个网络与之前基于DNA的网络并不完全一致。地理隔离、种群规模小、等位基因多样性低以及种群间高度分化表明，奠基者事件和遗传漂变的反复发生在这个热带灌木复合体的进化过程中起到了重要作用。
