Service Evolution Biologique et Ecologie, CP160/12, Faculté des Sciences, Université Libre de Bruxelles, 50 Av. F. Roosevelt, 1050 Brussels, Belgium.
Mol Phylogenet Evol. 2012 Jan;62(1):275-85. doi: 10.1016/j.ympev.2011.09.020. Epub 2011 Oct 14.
Plant species delimitation within tropical ecosystems is often difficult because of the lack of diagnostic morphological characters that are clearly visible. The development of an integrated approach, which utilizes several different types of markers (both morphological and molecular), would be extremely useful in this context. Here we have addressed species delimitation of sympatric tropical tree species that belong to Carapa spp. (Meliaceae) in Central Africa. We adopted a population genetics approach, sampling numerous individuals from three locations where sympatric Carapa species are known to exist. Comparisons between morphological markers (the presence or absence of characters, leaf-shape traits) and molecular markers (chloroplast sequences, ribosomal internal transcribed spacer region (ITS) sequences, and nuclear microsatellites) demonstrated the following: (i) a strong correlation between morphological and nuclear markers; (ii) despite substantial polymorphism, the inability of chloroplast DNA to discriminate between species, suggesting that cytoplasmic markers represent ineffective DNA barcodes; (iii) lineage sorting effects when using ITS sequences; and (iv) a complex evolutionary history within the genus Carapa, which includes frequent inter-specific gene flow. Our results support the use of a population genetics approach, based on ultra-polymorphic markers, to address species delimitation within complex taxonomic groups.
在热带生态系统中进行植物种的划分通常很困难，因为缺乏明显可见的诊断形态特征。在这种情况下，采用综合方法，利用多种不同类型的标记（形态和分子标记）将非常有用。在这里，我们研究了属于中美洲楝科（Meliaceae）的 Carapa 属的同域热带树种的物种划分。我们采用了种群遗传学方法，从已知存在同域 Carapa 物种的三个地点采集了许多个体。形态标记（特征的有无、叶形特征）和分子标记（叶绿体序列、核糖体内部转录间隔区（ITS）序列和核微卫星）之间的比较表明：（i）形态和核标记之间存在很强的相关性；（ii）尽管存在大量多态性，但叶绿体 DNA 无法区分物种，表明细胞质标记代表无效的 DNA 条形码；（iii）使用 ITS 序列时存在谱系分类效应；（iv）Carapa 属内的进化历史复杂，包括频繁的种间基因流。我们的结果支持使用基于超多态性标记的种群遗传学方法来解决复杂分类群中的物种划分问题。
