Molecular Phylogenetic Analyses: Gastropoda(Mollusca) And Its Lineage Of Cypraeidae

Gastropoda is one of the largest group of molluscs and even the whole animal kingdom. The facts of their long evolutionary history, very fast radiations, convergent and divergent evolutions, have made their origins and phylogenetic relationships one of the most controversial issues in the studies of zoology and evolutionary biology. Gastropoda's systematics has seen a recent boost from the end of last century, with the rapid developments of morphology and molecular biology technologies as well as the application of new systematic classification methods. However, a consistent opinion about their taxonomic systems have not been reached up to date and much more research work needs to be done in the future.The fragments of mtDNA COI gene were sequenced for 11 species from 3 subfamilies of Cypraeidae, and the homologous sequences of another 17 species of Cypraeidae were downloaded from GenBank. After the multiple sequence alignments, the sequence variation analyses were conducted and the molecular phylogenetic trees of Cypraeidae were reconstructed with NJ, MP and bayesian methods, using Prosimnia semperi of Cypraeacea as an outgroup. The sequence variation analyses showed that there are 236 variable and 221 parsimony-informative in the aligned 605 nucleotide sites, in addition, the relative frequenencies of four nucleotides were not equal an this fact showed that the base compositions were biased. The results of phylogenetic analyses showed: (1) the phylogenetic relationships of the Cypraeidae taxa was basically in consistent with morphology-based ones; (2)Cypraeovulinae was monophyletic in all trees, whereas Nariinae and Cypraeinae were not; (3)the monophylies of Mauritia, Palmadusta, Erosaria, Monetaria, Staphylaea and Pustularia were strongly supported by molecular data; (4)Meyer's speculation that Chelycypraea came out from Luria were also supported. Meanwhile, the phylogenetic relationships of Chelycypraea with Lyncina and the phylogenetic positions of this two groups await more detailed investigations.This study also attempted to tackle the systematic problems concerning gastropods, based on the nuclear LSU rRNA (28S rRNA) genes. Upon the aligned...