Studies On The Phylogeny Of Recent Ostracods And Its Community Structure From Lake Tai In China

Ostracod is one of the largest group of the Crustacea, and the number of the existing species of ostracods consists of 7 500. One of the frustrating aspects for Ostracoda study is unstable in the higher classification status, which might be related to the difficulty in comparing the characteristics of fossils and living forms. One of the aims of the present study is to reveal the evolutionary relationships of ostracods as well as to provide new evidences for further study of crustacean, and even for the arthropod. In addition, ostracods may be excellent organisms to be used as indicators of water quality, but such an idea requires detailed knowledge about their ecology, biology, and habitat requirements. However, so far as we know, very few studies have dealt with the relationship between the water quality and the ostracods, especially in China, and even some mistaken conclusions have been demonstrated about Lake Tai. The lake is the third biggest fresh-water lake in China and plays an important role in irrigation and drinking water. Therefore, one of the objectives of the present study is also to further understand the composing of ostracods and the relationship between ostracods and environment factors in Lake Tai.In the study on phylogenetic relationship of ostracods, three methods (maximum-likelihood, maximum-parsimony, and bayesian index) were used to generate a phylogenetic hypothesis by using ribosomal DNA sequences and some morphologic characters of the specimens covered all crustacean and hexopod. According to the results, we interpreted the phylogenetic relationships between ostracods and other "paucrustaceans", the phylogenetic relationships among ostracods, and the classification of ostracods. They revealed:1. Ostracoda was not monophyletic group, and the results suggested an early divergence between podocopan and myodocopan lineages. Obviously, Podocopa which covered cypridocopinan. dawinulocopinan, bairdiocopinan, cytherocopinan, and cytherllidaen was monophyletic assemblages; Myodocopa covering...