台灣及鄰近地區鈍頭蛇屬系統分類研究

Taxonomic review of the genus Pareas (Serpentes: Pareatidae) of Taiwan and the adjacent areas.

游崇瑋(Chung-Wei You)

指導教授 ： 林思民

國立臺灣師範大學/理學院/生命科學研究所/碩士(2011年)

摘要

鈍頭蛇科（Pareatidae）是近年由黃頷蛇科（Colubridae）中獨立的類群，由於擁有特化的食蝸食性，在生態、行為與演化上均具有高度的研究價值。在20世紀早期，Van Denburgh以及牧茂市郎先後發表台灣鈍頭蛇（Amblycephalus formosensis）以及駒井氏鈍頭蛇（A. komaii），兩者皆為台灣特有種。其後在1931年經歷了分類變革，鈍頭蛇屬的學名從原先的Amblycephalus改成Pareas。1997年，日籍學者太田英利教授認為台灣只產有一種鈍頭蛇，而根據命名法則稱作較早發表的名稱：台灣鈍頭蛇（Pareas formosensis）。然而，近來我們發現台灣的鈍頭蛇中存在著不連續的外部型態差異，顯見此類群在分類上仍有待釐清。為了探討台灣及鄰近地區鈍頭蛇的系統分類及演化關係，我們同時進行外部型態的檢測及遺傳的分析，並納入產於沖繩的八重山鈍頭蛇（P. iwasakii）進行比對。外部形值方面，我們記錄了身長各項比例、鱗脊、鱗片數量、眼色等數據。遺傳標記方面，則利用PCR增幅粒線體cytochrome b及核染色體的c-mos基因片段，並利用序列建構親緣關係樹。結果從粒線體DNA的序列中發現台灣至少存在三個遺傳上差異明顯的系群，彼此並不成為單系群。其中，台灣鈍頭蛇（P. formosensis）和漢氏鈍頭蛇（P. hamptoni）聚合為遺傳距離非常相近的一群，屬同種範圍。根據漢氏鈍頭蛇的原始描述文獻，我們發現漢氏鈍頭蛇和台灣鈍頭蛇在背部鱗片上有些許差異，據此我們建議將台灣鈍頭蛇歸於漢氏鈍頭蛇的一個亞種（P. hamptoni formosensis）。由核染色體的遺傳標記顯示台灣島內的鈍頭蛇即使處於共域分布的地區，也完全沒有任何的遺傳交流，而且三者均具備可資明顯鑑別的外部形態特徵。由於多組證據相互吻合，我們認為台灣的鈍頭蛇總共存在三個有效的分類群。比對正模標本的外部形值之後，我們認為駒井氏鈍頭蛇應該回復為一個有效種，意即，台灣目前存有三種鈍頭蛇：漢氏鈍頭蛇台灣亞種，駒井氏鈍頭蛇，以及一個未發表的隱藏種。

關鍵字

分類學 ； 系統分類學 ； 系統演化學 ； 鈍頭蛇 ； 隱藏種

並列摘要

Pareatidae is a group of snail-eating or slug-eating snakes recently separated from Colubridae. Due to its specialized feeding habit, Pareatidae is an extremely interesting taxon in researches concerning ecology, behavior and evolutionary biology. In the early 20th century, Van Denburgh and Maki described the first and the second pareatid snakes of Taiwan as Amblycephalus formosensis and A. komaii, respectively. In 1931, the genus name was changed from Amblycephalus to Pareas. However, after an examination including museum specimens of both species, Ota (1997) concluded only one species of Pareas occurs in Taiwan, i.e., the earlier published species P. formosensis. However, discovery of some discrete morphological differences within this species in recent years indicated that taxonomy of Pareas snakes in Taiwan remains a controversial issue. In order to clarify the taxonomic status and phylogenetic relationships of Pareas snakes among Taiwan and neighboring regions, we performed morphological inspections and genetic analyses. From mtDNA cyt b tree, we found three distinct clades within Taiwanese pareatids, which do not form a monophyletic group when sequences of outgroup species were included. The genetic distances among the three Taiwanese clades are even larger than that compared to P. iwasakii or other outgroup speices. Otherwise, it was unexpected that P. formosensis grouped with P. hamptoni, and according to the original description of P. hamptoni, there are differences on dorsal scale counts between the two species, thus we suggest it to be considered a subspecies of P. hamptoni, i.e. Pareas hamptoni formosensis. The consistent tree topology between mitochondrial and nuclear markers, along with the congruence clade allocation of all individuals examined in sympatric localities indicated that there were no gene flow among different clades. In addition, all the three clades could be identified by their own morphological characteristics. Because of the multiple and consistent sets of evidences, we predicted the existence of three valid species of pareatid snakes in Taiwan. After we compared morphological data of the holotype and paratype, we consider Pareas komaii should be revived as a valid species. Conclusively, three Pareas snakes currently exist in Taiwan, including P. hamptoni formosensis, P. komaii and an undescribed cryptic species.

並列關鍵字

taxonomy ； systematics ； phylogeny ； Pareas ； cryptic species

參考文獻

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