PDF(Pubmed)
Abstract：
Using the genus Casearia, we assessed the status of nested singletons: individual specimens corresponding to accepted species but in molecular trees appearing nested within clades of closely related species. Normally, such cases would be left undecided, while on the other hand, timely taxonomic decisions are required. We argue that morphological, chorological, and ecological data can be informative to illuminate patterns of speciation. Their use can provide a first step in testing taxon concepts at species level. We focused on five cases of nested singletons in trees of the genus Casearia. We employed PCA and cluster analysis to assess phenotypic differentiation. Using geocoordinates, we calculated niche space differentiation based on 19 bioclim variables, by means of PCA and niche equivalency and similarity tests and generated dot maps. We found that the singletons were morphologically distinctive in two of the five cases (Casearia selloana and C. manausensis), relatively distinctive in two other cases (C. zizyphoides and C. mariquitensis), and partially overlapping in the last case (C. grandiflora). For two cases (C. mariquitensis and C. selloana), ecological niche space was broadly overlapping, in two cases it was found broadly nested (C. grandiflora and C. zizyphoides), and in one case narrowly nested (C. manausensis), but in no case niche differentiation was observed. Niche overlap, similarity and equivalency showed corresponding patterns. Given these data, one would interpret C. selloana and C. manausensis as presumably well-distinguished taxa, their narrow distribution ranges suggesting recently emerging lineages. The other three cases are not clearcut. Morphological data would suggest particularly C. grandiflora conspecific with C. arborea, but differences in the distribution are intriguing. Our approach would reject the notion of potential synonymy based on nested phylogenetic placement for at least two of the five cases. The other case also shows no complete lack of differentiation which would support synonymy.
摘要：
使用Casearia属，我们评估了嵌套单体的状态：单个标本对应于可接受的物种，但在分子树中出现嵌套在密切相关物种的进化枝中。通常,这种情况将悬而未决，而另一方面,需要及时的分类学决策。我们认为形态学上，脉络膜,生态数据可以提供信息来阐明物种形成的模式。它们的使用可以提供在物种水平上测试分类单元概念的第一步。我们重点研究了Casearia属树木中的5例嵌套单例。我们采用PCA和聚类分析来评估表型分化。使用地理坐标，我们基于19个生物环境变量计算了生态位空间分化，通过PCA和生态位等效性和相似性测试，并生成了点图。我们发现五个病例中的两个（Caseariaselloana和C.manausensis）在形态上是独特的，在另外两种情况下相对不同(C.zizyphoides和C.maritquensis)，在最后一种情况下部分重叠(C.grandiflora）。对于两种情况(C.大麻和C.selloana)，生态位空间广泛重叠，在两种情况下，它被发现是广泛嵌套的(C.花兰和花兰），在一种情况下，窄嵌套(C.manausensis)，但在任何情况下都没有观察到生态位分化。利基重叠，相似性和等效性显示出相应的模式。鉴于这些数据,人们会将C.selloana和C.manausensis解释为很好的分类群，他们狭窄的分布范围表明最近出现的血统。其他三种情况不清楚。形态学数据将特别表明C.grandiflora与C.arborea，但是分布的差异很有趣。我们的方法将在五个案例中的至少两个案例中拒绝基于嵌套系统发生位置的潜在同义词的概念。另一种情况也显示出没有完全缺乏支持同义词的区分。
