臺灣地區樹棲性南亞蝸牛科白高腰蝸牛群系統分類與親緣關係研究

Systematics and Phylogeny of the Arboreal Snail Satsuma albida (Pulmonata: Camaenidae) Species Complex from Taiwan

吳書平(Shu-Ping Wu)

指導教授 ： 林曜松

國立臺灣大學/生命科學院/生態學與演化生物學研究所/博士(2007年)

https://doi.org/10.6342/NTU.2007.00767

摘要

摘要

本論文旨在探討台灣地區南亞蝸牛科栗蝸牛屬之一樹棲群，白高腰蝸牛與其近緣種之系統分類與親緣關係。所有本島栗蝸牛屬物種之親緣關係亦予檢視，以分子證據重建其演化史與探究其種化機制。

第一章對南亞蝸牛科之系統分類特徵及與台灣本科動物相相關之分類爭議與研究史予以簡介。

第二章針對樹棲種群白高腰蝸牛與其近似種進行詳盡模式標本檢視，並由模式產地採集證據標本供分子分析，本研究選取之分子標記為粒線體 DNA CO 1 基因片段序列。對於本島各地採取之所有近似種類進行生殖系統之比較解剖與分子親緣分析後，原本認定為白高腰蝸牛亞種的奇異高腰蝸牛與艷美高腰蝸牛應提升為獨立種，而在全島各地採集之近似於白高腰蝸牛的類群共鑑識出 14 個新種，這些新種具有地理分布與棲地上的侷限性，皆為樹棲、夜行與植食性種類，遺傳結構與生殖系統型態上具有明顯特徵足堪辨識。

第三章以一種廣布的地棲性栗蝸牛為研究對象，探討其族群遺傳結構並藉此偵測隱蔽種。栗蝸牛是廣泛分布於臺灣西部地區的地棲性特有種南亞蝸牛。利用粒線體 DNA CO 1 基因序列片段，分析來自 11 個樣點 68 隻栗蝸牛個體，探討其族群遺傳結構。結果顯示栗蝸牛分為北、中、南三大群，各群有其遺傳特色且群間無明顯基因交流。遺傳多樣性以南部群最高，新竹地區的北部群最低且與其他二群遺傳距離最遠。此外，於高雄、屏東、花蓮及台東等地採集之栗蝸牛亞種與外形相似之種類，遺傳與親緣分析皆顯著異於栗蝸牛，屬於不同物種。

第四章探討台灣產南亞蝸牛科的詳盡親緣關係與演化史，所有本島產本科物種皆予以討論。本研究利用粒線體 DNA CO 1 與 16S rRNA 以及核基因 ITS 等基因序列片段為分子標記，結果顯示本科栗蝸牛屬內物種種化的機制複雜，包含空間分化之後生態棲位改變導致之種化事件；單基因突變造成殼體對稱旋性反轉而引起之種化；以及地理空間上長期發生之擴散分化或分裂分化導致之種化事件，顯示在一封閉島嶼的屬內種化事件仍可能由多起源因素所致。

關鍵字

南亞蝸牛科 ； 系統分類 ； 親緣關係

並列摘要

ABSTRACT

This dissertation concerns the systematics and phylogeny of a genus Satsuma (Pulmonata: Camaenidae) land snail group, Satsuma albida and its akin species from Taiwan. The phylogenetic relationships of the whole Satsuma species on this island are discussed in order to confer the evolutionary history and mechanism of their species formation.

In the Chapter One, a general introduction is given on the systematics of the Camaenidae family. Taxonomy of species, studies of history and classification controversy in this group from Taiwanese camaenids fauna are also discussed.

In the Chapter Two, the author apply traditional taxonomy method as comparative anatomy of the genital system, with the molecular survey was used to probe into the phylogenetic relationships of an arboreal Satsuma species complex from Taiwan, called Satsuma albida species complex. In this study, fifteen species were identified and described as new species from the group. Two subspecies of S. albida, S. a. insignis and S. a. mollicula were promoted to an independent species based on the characters of their reproductive system and the molecular phylogenetic relationships from other taxa. The reasons of species formation are also discussed, which provide more evolutionary evidences of the Satsuma snails from Taiwan.

In the Chapter Three, the author used partial sequences of mtDNA CO 1 gene was used as the molecular marker to survey the population genetic structure of the terrestrial endemic Satsuma species, S. nux and its subspecies, which is widely distributed around Taiwan. After employing the molecular analysis, the true S. nux, which were conformed to the type specimen, were proved that only distributed in lowland areas of western Taiwan. Other S. nux like species should be recognized as independent species. It means that they are cryptic species of S. nux. Other two subspecies of S. nux, S. n. paiwanis and S. n. litus should seem as independent species as well. But the subspecies S. n. sericata is a synonym of S. nux according to the close genetic distance and similarity in the genetic structure to the S. nux population. The population genetic structure of S. nux can be divided into three deep clades, each group provides with unique haplotypes that are not shared between groups. These three groups may have diverged a long time ago via retreat and expansion events from different genetic sources several times.

In the Chapter Four, an explicit phylogenetic relationship of all Taiwanese Camaenidae land snails are shown, which is based on the molecular markers of mtDNA and nucleus genes reflecting their evolutionary history. Species formation can be promoted via ecological reasons, such as spatial allocation in the group of arboreal species; or via single-gene mutation such as chiral reverse from sinistral to dextral shells. Such can cause mismatch mating and procure incipient species formation. Speciation can also be happened with a long term evolutionary process, through the vicariance or dispersal events and cause a monophyletic clade within high diversity taxa on the species level. Thus, these snails revealed a multiple origin of incipient speciation motive force within a genus even though confined through an island.

並列關鍵字

Camaenidae ； systematics ； phylogeny

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