Paquin P, Hedin M
Department of Biology, San Diego State University, San Diego, CA 92812-4614, USA.
Mol Ecol. 2004 Oct;13(10):3239-55. doi: 10.1111/j.1365-294X.2004.02296.x.
Rapid development in karst-rich regions of the US state of Texas has prompted the listing of four Cicurina species (Araneae, Dictynidae) as US Federally Endangered. A major constraint in the management of these taxa is the extreme rarity of adult specimens, which are required for accurate species identification. We report a first attempt at using mitochondrial DNA (mtDNA) sequences to accurately identify immature Cicurina specimens. This identification is founded on a phylogenetic framework that is anchored by identified adult and/or topotypic specimens. Analysis of approximately 1 kb of cytochrome oxidase subunit I (CO1) mtDNA data for over 100 samples results in a phylogenetic tree that includes a large number of distinctive, easily recognizable, tip clades. These tip clades almost always correspond to a priori species hypotheses, and show nonoverlapping patterns of sequence divergence, making it possible to place species names on a number of immature specimens. Three cases of inconsistency between recovered tip clades and a priori species hypotheses suggest possible introgression between cave-dwelling Cicurina, or alternatively, species synonymy. Although species determination is not possible in these instances, the inconsistencies point to areas of taxonomic ambiguity that require further study. Our molecular phylogenetic sample is largest for the Federally Endangered C. madla. These data suggest that C. madla occurs in more than twice the number of caves as previously reported, and indicate the possible synonymy of C. madla with C. vespera, which is also Federally Endangered. Network analyses reveal considerable genetic divergence and structuring across caves in this species. Although the use of DNA sequences to identify previously 'unidentifiable' specimens illustrates the potential power of molecular data in taxonomy, many other aspects of the same dataset speak to the necessity of a balanced taxonomic approach.
美国得克萨斯州岩溶丰富地区的快速发展促使四种圆蛛属物种（蜘蛛目，皿蛛科）被列为美国联邦濒危物种。对这些分类单元进行管理的一个主要限制因素是成年标本极其罕见，而准确鉴定物种需要成年标本。我们报告了首次尝试使用线粒体DNA（mtDNA）序列来准确鉴定未成熟的圆蛛属标本。这种鉴定基于一个系统发育框架，该框架以已鉴定的成年和/或模式标本为基础。对100多个样本的约1 kb细胞色素氧化酶亚基I（CO1）mtDNA数据进行分析，得到了一棵系统发育树，其中包含大量独特的、易于识别的末端分支。这些末端分支几乎总是与先验的物种假设相对应，并显示出不重叠的序列分歧模式，从而有可能为许多未成熟标本确定物种名称。在恢复的末端分支与先验物种假设之间存在三例不一致的情况，这表明穴居圆蛛属物种之间可能存在基因渗入，或者存在物种同义现象。尽管在这些情况下无法确定物种，但这些不一致之处指出了分类学上存在歧义的领域，需要进一步研究。我们的分子系统发育样本对于联邦濒危物种马德拉圆蛛来说是最大的。这些数据表明，马德拉圆蛛出现的洞穴数量是此前报道数量的两倍多，并表明马德拉圆蛛可能与同样为联邦濒危物种的韦氏圆蛛同义。网络分析揭示了该物种在不同洞穴之间存在相当大的遗传差异和结构分化。尽管使用DNA序列来鉴定以前“无法鉴定”的标本说明了分子数据在分类学中的潜在作用，但同一数据集的许多其他方面也表明了采用平衡分类方法的必要性。
