Cyclophoridae phylogeny and the speciation events of Cyclophorus and Cyclotus taivanus ssp.

[[abstract]]Cyclophoridae consists of four subfamilies and about 300 species currently arranged in 38 genera, occuping varies habitats, with great morphological diversity allover the world. However, the relationship among Cyclophoridae is thus far not clear. In order to investigate this, I sampled cyclophorid snails around Taiwan and its adjacent areas, and then sequenced part of the mitochondrial COI (cytochrome oxidase subunit I) and the 16S rRNA gene from 32 species of 10 cyclophorid genera to establish a phylogenetic tree of Cyclophoridae. Phylogenetic relationships based on mtDNA sequences suggest that Cyclophorus, Cyclotus, Leptopoma, and Platyrhaphe are monophyletic while the traditional genus Japonia is polyphyletic, and the previous J. zebra should be placed into a new genus Pilosphaera. In addition, Pilosphaera yentoensis n. sp. and Japonia boonkioensis n. sp. will also be described as new species. Members of Cyathopoma are tiny white cyclophorid snails occurring in East Asia, Madagascar and the Seychelles. Phylogenetic relationships of Cyathopoma are uncertain. Combined with COI and radular data, I conclude that Cyathopoma and Cyclotus are only distantly related. Cyathopoma iota has been considered to be a controversial member of this group. Through molecular and radular data, I found C. iota to be closer to C. taiwanicum than to C. micron, and concluded that C. micron, C. ogaitoi, C. iota and C. taiwanicum all belong to Cyathopoma. There are 10 genera and 29 cyclophorid species in Taiwan. Among them, the most interesting taxa are Cyclophorus and Cyclotus, both sharing similar ecological niches and representing by a north and south form in morphology. In order to clarify their relationship, I have to find out their sister group as out groups to compare with the members among Cyclophorus and Cyclotus. The gene trees of Cyclophoridae indicate that Japonia and Pterocyclus are sister group of Cyclophorus and Cyclotus, respectively. The former two will be used as the out groups of Cyclophorus and Cyclotus in their phylogenetic studies. Both COI and 16S rRNA gene trees of Taiwan Cyclophorus show prominent geographic structure. The Mantel test showed significant positive correlation between fixation index (FST) and cumulative geographic anti-clockwise distance (origin in the region around Tainan, anti-clockwise pass through south cape, Taidung, Hualian, Iran, Taipei, Taichung and meet the original populations in Jia-yi). There are finite gene flew between adjacent populations. And there are series of clines around the Central Range. Cyclophorus of Taiwan is a proposed “ring species”. In the morphology and environmental variables correlation study, I found the currently shell morphology may be caused by the adaptations of recent long term climate. In traditional classification, Cyclotus taivanus consists of five subspecies, with clear morphological diversity. The molecular phylogenetic relationships of this group have never been discussed before. I sequenced part of the mitochondrial COI (cytochrome oxidase subunit I) and the 16S rRNA gene from 27 sampling sites. I also measured 9 shell traits to investigate the relationships between C. taivanus ssp. Even though the morphology PCA revealed a more or less continuous distribution of individuals in morph-space, the two highly divergent haplotype clades in COI and 16S rRNA analysis indicated the presence of two independently evolving lineages. The sequence divergence between two clades was almost as high as between other Cyclophoridae species. Therefore C. adamsi should be a considered valid species. For the environmental analysis, temperature may be a limiting element to the distribution of C. adamsi and C. taivanus group. The ecological divergence probably is the ruling force of speciation in my case. The PLS analysis results indicate, that phenotypic plasticity may be a key element of variable shell in C. taivanus group. The ecological divergence probably appears rule of speciation in C. taivanus ssp. case. The speciation process may be incomplete among C. t. dilatus, C. t. diminutus, C. t. peraffinis, and C. t. taivanus, and the adaptation of climatic pressure continue being a rule of speciation process. This study provides an opportunity to understand that no matter how similar two taxonomic groups are, occupying similar niche, undergoing the same geology history, with morphological adaptation to the same long term climate, they may have different speciation model.