Forsman Zac H, Barshis Daniel J, Hunter Cynthia L, Toonen Robert J
Hawaii Institute of Marine Biology, Kaneohe, HI 96744, USA.
BMC Evol Biol. 2009 Feb 24;9:45. doi: 10.1186/1471-2148-9-45.
Corals are notoriously difficult to identify at the species-level due to few diagnostic characters and variable skeletal morphology. This 'coral species problem' is an impediment to understanding the evolution and biodiversity of this important and threatened group of organisms. We examined the evolution of the nuclear ribosomal internal transcribed spacer (ITS) and mitochondrial markers (COI, putative control region) in Porites, one of the most taxonomically challenging and ecologically important genera of reef-building corals.
Nuclear and mitochondrial markers were congruent, clearly resolving many traditionally recognized species; however, branching and mounding varieties were genetically indistinguishable within at least two clades, and specimens matching the description of 'Porites lutea' sorted into three genetically divergent groups. Corallite-level features were generally concordant with genetic groups, although hyper-variability in one group (Clade I) overlapped and obscured several others, and Synarea (previously thought to be a separate subgenus) was closely related to congeners despite its unique morphology. Scanning electron microscopy revealed subtle differences between genetic groups that may have been overlooked previously as taxonomic characters.
This study demonstrates that the coral skeleton can be remarkably evolutionarily plastic, which may explain some taxonomic difficulties, and obscure underlying patterns of endemism and diversity.
由于诊断特征稀少且骨骼形态多变，珊瑚在物种层面极难鉴定。这种“珊瑚物种问题”阻碍了我们对这一重要且濒危生物群体的进化和生物多样性的理解。我们研究了鹿角珊瑚属（Porites）中核糖体核糖核酸内转录间隔区（ITS）和线粒体标记（COI、假定控制区）的进化，鹿角珊瑚属是造礁珊瑚中分类学上最具挑战性且生态上最重要的属之一。
核标记和线粒体标记结果一致，清晰地分辨出许多传统上认可的物种；然而，在至少两个进化枝中，分支和丘状变种在基因上无法区分，且符合“黄鹿角珊瑚（Porites lutea）”描述的标本被分为三个基因差异较大的组。珊瑚单体水平的特征通常与基因分组一致，尽管其中一组（进化枝I）的高度变异性与其他几组重叠并掩盖了它们，并且联合珊瑚属（Synarea，以前被认为是一个单独的亚属）尽管形态独特，但与同属物种关系密切。扫描电子显微镜揭示了基因分组之间的细微差异，这些差异以前可能被忽视作为分类特征。
本研究表明珊瑚骨骼在进化上可能具有显著的可塑性，这可能解释了一些分类学上的困难，并掩盖了潜在的特有性和多样性模式。
