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

• Main Authors: Shu-Ping Wu, 吳書平
• Other Authors: Yao-Sung Lin
• Format: Others
• Language: en_US
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/85058271820412621058

博士 === 國立臺灣大學 === 生態學與演化生物學研究所 === 95 === 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.