Departamento de Botânica, Instituto de Biologia, Universidade Estadual de Campinas, Cx.P. 6109, Campinas-SP, 13083-970, Brazil; and.
Am J Bot. 2001 Mar;88(3):419-28.
We conducted an isozyme study in 22 populations of five Pleurothallis (Orchidaceae) species (12 loci in nine enzymatic systems). The genetic variability in all populations is surprisingly high (P = 58-83%, A = 2.1-3.8, H(e) = 0.25-0.43) in spite of the fact that the five species are pollinated by small flies whose behavior enables self-pollination. We suggest that self-incompatibility, inbreeding depression, and mechanical barriers that prevent self-pollination in these species are responsible for the maintainance of the high genetic variability. These traits are uncommon in Orchidaceae, but have been observed in these and some other species pollinated by flies or other pollinators with behavior that facilitates self-pollination. The genetic similarity among conspecific populations is also high for species with very short-range flying pollinators. Only one population of P. teres presented values of genetic similarity lower than usually observed in allopatric conspecific populations. Morphology, however, does not support its segregation as a new taxon. All species can be recognized by their enzymatic patterns, and the results agree with recently proposed taxonomic realignments. Conversely, the supposed affinities among these species based on floral morphology are not supported, and we hypothesize that it may be due to convergence in species with similar pollinators.
我们对五个 Pleurothallis（兰科）物种的 22 个种群进行了同工酶研究（九个酶系统中的 12 个基因座）。尽管这五个物种是由小型苍蝇授粉的，而苍蝇的行为可以使其进行自花授粉，但所有种群的遗传变异性都非常高（P = 58-83%，A = 2.1-3.8，H(e) = 0.25-0.43）。我们认为，自交不亲和、近交衰退和阻止这些物种自花授粉的机械障碍是维持高遗传变异性的原因。这些特征在兰科植物中并不常见，但在这些物种和其他一些由苍蝇或其他具有促进自花授粉行为的传粉者授粉的物种中观察到了这些特征。对于具有短程飞行传粉者的同种种群，其遗传相似性也很高。只有一个 P. teres 种群的遗传相似性值低于同域同种种群通常观察到的值。然而，形态学并不能支持其作为一个新分类群的分离。所有物种都可以通过其酶谱来识别，并且结果与最近提出的分类重新调整一致。相反，基于花形态的这些物种之间的假定亲缘关系不被支持，我们假设这可能是由于具有相似传粉者的物种的趋同进化造成的。
