Evolution, Ecology and Genetics, Research School of Biology, The Australian National University, Canberra, ACT, 0200, Australia.
Mol Ecol. 2012 Nov;21(21):5208-20. doi: 10.1111/mec.12036. Epub 2012 Sep 27.
A leading hypothesis for the immense diversity of the Orchidaceae is that skewed mating success and small, disjunct populations lead to strong genetic drift and switches between adaptive peaks. This mechanism is only possible under conditions of low gene flow that lead to high genetic differentiation among populations. We tested whether orchids typically exhibit high levels of population genetic differentiation by conducting a meta-analysis to compare mean levels of population genetic differentiation (F(ST)) between orchids and other diverse families and between rare and common orchids. Compared with other families, the Orchidaceae is typically characterized by relatively low genetic differentiation among populations (mean F(ST) = 0.146) at allozyme loci. Rare terrestrial orchids showed higher population genetic differentiation than common orchids, although this value was still lower than the mean for most plant families. All lines of evidence suggest that orchids are typically characterized by low levels of population genetic differentiation, even in species with naturally disjunct populations. As such, we found no strong evidence that genetic drift in isolated populations has played a major role in the diversification of the Orchidaceae. Further research into the diversification of the family needs to unravel the relative roles of biotic and environmental selective pressures in the speciation of orchids.
兰花科巨大多样性的一个主要假说认为，交配成功率的偏斜和小而分散的种群导致了强烈的遗传漂变和适应峰之间的转换。这种机制只有在基因流低的条件下才有可能发生，这种条件会导致种群之间的遗传分化很高。我们通过进行荟萃分析来比较兰花和其他多样化的科之间以及稀有兰花和常见兰花之间种群遗传分化（F(ST)）的平均水平，以检验兰花是否通常表现出高水平的种群遗传分化。与其他科相比，兰花科在等位酶位点上的种群遗传分化通常相对较低（平均 F(ST) = 0.146）。与常见兰花相比，稀有陆生兰花的种群遗传分化更高，但这个值仍然低于大多数植物科的平均值。所有证据表明，兰花通常表现出低水平的种群遗传分化，即使在种群自然分散的物种中也是如此。因此，我们没有发现强有力的证据表明遗传漂变在孤立的种群中在兰花科的多样化中起了主要作用。进一步研究该科的多样化需要阐明生物和环境选择压力在兰花物种形成中的相对作用。
