以多組分子遺傳標誌探討表孔珊瑚屬的分子親緣關係

表孔珊瑚屬為造礁珊瑚中的第二大屬，包含了七十五種。由於種類數多，過去的學者在進行表孔珊瑚分類時，通常先將形態相似的物種分成不同的種群，而這些種群基本上不具有分類上的意義。表孔珊瑚種群的特徵是依據珊瑚共骨的細微骨骼構造或是以珊瑚群體的生長型來分群。珊瑚共骨結構包含平凹狀、針狀、管狀以及疣狀共四類，珊瑚群體的生長型包含葉片狀、匍匐或團塊狀以及分枝狀共三類。然而，依據共骨結構或是生長型所分出的種群，在過去的文獻結果具有很大的差異。另外，同一株珊瑚群體常同時具有不同生長型，常造成分類鑑定上的困擾。本研究採集產於台灣海域的三十二種表孔珊瑚，利用三組獨立的分子遺傳標誌，包括粒線體第三基因區間、調鈣蛋白基因第二介入子以及核糖體轉錄區間，建構表孔珊瑚屬的巢狀系群分析及分子親緣關係樹，驗證以珊瑚共骨結構以及生長型為依據的分類群假說。分析結果顯示，粒線體第三基因區間的巢狀系群分析可將疣狀共骨與其他共骨結構區分出不同系群，而其親緣關係樹則可分出平凹狀、疣狀，以及針狀與管狀混合的三系群。調鈣蛋白基因第二介入子的巢狀系群分析與親緣關係樹區分出三個共骨形態系群，疣狀與平凹各自獨立成一個系群，而針狀與管狀則混合於另外的系群。但是在核糖體轉錄區間的親緣關係樹只能區分出平凹狀的系群。這些分群現象的差異可能肇因於此三組標誌具有不同的分子演化特性。然而，三組分子遺傳標誌得到共同的分子親緣分析無法支持以生長型為依據的種群假說。相反的，除了少數的例外，分子親緣研究結果傾向支持以共骨結構為依據的種群假說，進一步證明共骨結構不僅在分類上具有明顯的貢獻，同時也具有親緣上的意義。重整過去的文獻與本研究的結果，未來表孔珊瑚屬可以依據平凹狀、針管狀及疣狀三群主要共骨結構進行種群的分類。

關鍵字

表孔珊瑚；分子親緣關係；造礁珊瑚

並列摘要

Montipora is the second speciose genus of scleractinians with 75 species currently described. In order to accommodate this speciose genus, species groups were adopted to cluster morphologically similar species based on either the final skeleton structure of coenosteums or the colony growth forms. These conventional groupings, however, do not imply any taxonomic affinity. Four major coenosteums and three growth forms including, glabrous-foveolate, papillae, tuberculae, verrucae, and laminar, encrusting-massive, and branches were used, either respectively or jointly, to define the species groups and species in the literatures. However, the results were usually conflict. In addition, more than one growth form was often observed within a single colony that confused identification of Montipora. In this study, we examined two taxonomical grouping hypotheses: (1) coenosteum hypothesis, groups based on glabrous-foveolate, papillae, tuberculae and verrucae, and (2) growth form hypothesis, groups based on laminar, encrusting-massive, and branches. Molecular phylogenies of 32 Montipora species were constructed using three independent loci, including mitochondrial intergenic region 3 (mtigr3, 472bp) spanning between cytochrome b (Cytb) and NADH dehydrogenase subunit 2 (ND2) genes, nuclear ribosomal internal transcribed spacer (ITS; ITS1+ITS2, 393bp), and an intron spanning between exon 2 and 3 of the calmodulin gene (CaM-II, 270bp). Species phylogeny analysis of the three independent loci using nested clade analysis (NCA) and phylogenetic trees with neighbour-joining, maximum-parsimony, maximum-likelihood, and Bayesian-likelihood approaches were largely corresponded with coenosteum structures groups, but not with growth forms. The NCA and phylogenetic trees based on mtigr3 and CaM-II loci could distinguish three coenosteum monophyletic groups consisted of “glabrous-foveolate”, “papillae-tuberculae” and “verrucae”, but the ITS can only divided glabrous-foveolate coenosteum from the others. Combining the three molecular markers suggested that growth forms did not contribute to resolve the taxonomic complexity of species groups for genus Montipora. Instead, with a few exceptions, the phylogenetic analyses tended to support the grouping based on coenosteum structures, which divided the genus into three major groups, included glabrous-foveolate, papillae-tuberculae and verrucae. This result highlighted not only the phylogenetic significance but also the utility of coenosteum structures in the future revision of species group and species taxonomy in genus Montipora.

並列關鍵字

Scleractinia ； molecular phylogeny ； Montipora

參考文獻

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以多組分子遺傳標誌探討表孔珊瑚屬的分子親緣關係

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