Verbruggen Heroen, Clerck Olivier De, Schils Tom, Kooistra Wiebe H C F, Coppejans Eric
Phycology Research Group and Center for Molecular Phylogenetics and Evolution, Ghent University, Krijgslaan 281 (S8), B-9000 Gent, Belgium.
Mol Phylogenet Evol. 2005 Dec;37(3):789-803. doi: 10.1016/j.ympev.2005.06.015. Epub 2005 Aug 10.
Nuclear ribosomal and plastid DNA sequences of specimens belonging to section Halimeda of the pantropical green seaweed genus Halimeda show that the group under scrutiny contains many more genetically delineable species than those recognized by classical taxonomy. Discordances between phylograms inferred from nuclear and plastid DNA sequences suggest that reticulate evolution has been involved in speciation within the clade. Nonetheless, our data do not allow ruling out certain alternative explanations for the discordances. Several pseudo-cryptic species are restricted to the margins of the generic distribution range. In a clade of H. cuneata sibling species from widely separated subtropical localities in the Indian Ocean, the South African sibling branches off first, leaving the Arabian and West Australian species as closest relatives. We hypothesize that geographic isolation of the siblings may have taken place following Pleistocene or Pliocene periods of climatic cooling during which subtropical species occupied larger distribution ranges. A more basal separation of Atlantic, Indo-Pacific, and Mediterranean species indicates vicariance. The alternative events that could have caused this vicariance are discussed.
泛热带绿藻属仙掌藻（Halimeda）的哈氏仙掌藻组（section Halimeda）标本的核糖体DNA和质体DNA序列表明，与经典分类学所认定的物种相比，该研究组中在基因上可明确区分的物种要多得多。从核糖体DNA和质体DNA序列推断出的系统发育树之间的不一致表明，网状进化参与了该分支内的物种形成。尽管如此，我们的数据并不排除对这些不一致的某些其他解释。有几个假隐性物种仅限于该属分布范围的边缘。在来自印度洋广泛分离的亚热带地区的楔叶仙掌藻（H. cuneata）姐妹种的一个分支中，南非的姐妹种最先分化出来，而阿拉伯和西澳大利亚的物种则是其最近的亲缘种。我们推测，这些姐妹种的地理隔离可能发生在更新世或上新世气候变冷时期之后，在此期间亚热带物种占据了更大的分布范围。大西洋、印度-太平洋和地中海物种在更基部的分化表明了隔离分化。文中讨论了可能导致这种隔离分化的其他事件。
