Thistle be a mess: Untangling the taxonomy of Cirsium (Cardueae: Compositae) in North America
Thistle be a mess: Untangling the taxonomy of Cirsium (Cardueae: Compositae) in North America
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DOI：
10.1111/jse.12692
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发表时间：
2020-11-01
影响因子：
3.7
通讯作者：
Funk, Vicki A.
中科院分区：
文献类型：
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作者：
Ackerfield, Jennifer R.;Keil, David J.;Funk, Vicki A.
蓟（即“蓟”）是北美最具分类学挑战性的菊科类群之一。这项研究是首次尝试推断北美蓟的广泛采样系统发育。两个主要目标是：(i) 测试当前假设的物种多样性复合体（C. arizonicum、C. clavatum、C. eatonii 和 C. cariosum）是否构成单系谱系，以及 (ii) 重新划分任何被确定为有问题的类群。基于两个核核糖体区域的 DNA 序列数据和四个质体标记的系统发育重建被用来推断进化谱系并测试物种的界限。八个物种品种复合体被解析为多系。我们重新限制了这些复合体，并在此过程中找到了支持六种新分类群识别的证据。我们假设Cirsium中广泛的分类困难是由几个因素造成的：（i）以前未描述的分类群，（ii）植物标本中分类群的代表性不足，（iii）表型趋同，（iv）杂交，以及（v）早期物种形成。虽然我们可以提供证据来支持某些分类单元的重新划分，但其他分类单元仍然悬而未决。因此，我们正在对北美蓟进行系统发育学研究，以回答剩余的分类学问题，并为生物地理学研究提供强有力的框架。
Cirsium (i.e., "thistles") are one of the most taxonomically challenging groups of Compositae in North America. This study represents the first attempt to infer a broadly sampled phylogeny of Cirsium in North America. The two main objectives are to: (i) test whether currently hypothesized species variety complexes (C. arizonicum, C. clavatum, C. eatonii, and C. scariosum) constitute monophyletic lineages, and (ii) recircumscribe any taxa that are identified as problematic. Phylogeny reconstructions based on DNA sequence data from two nuclear ribosomal regions and four plastid markers were used to infer evolutionary lineages and test species' delimitations. Eight species varietal complexes were resolved as polyphyletic. We recircumscribed these complexes and in doing so found evidence to support the recognition of six new taxa. We hypothesize that the extensive taxonomic difficulty within Cirsium is the result of several factors: (i) previously undescribed taxa, (ii) inadequate representation of taxa from herbarium specimens, (iii) phenotypic convergence, (iv) hybridization, and (v) incipient speciation. While we can provide evidence to support the recircumscription of some taxa, others remain unresolved. Therefore, we are working on a phylogenomic study of North American Cirsium to answer remaining taxonomic questions as well as provide a robust framework for biogeographic studies.