|Other Abstract||The dissertation focused on the species classification and molecular systematics of two endangered commercial fish genera in China. We studied taxonomy of Cranoglanis Peters and phylogeny and biogeography of Coilia Gray by means of the morphological and molecular data, respectively. This paper’s content was divided into two main parts:
The genus Cranoglanis (Silurformes: Cranoglanididae) is a group of fishes occurring only in East Asia. They are distributed in the drainages of Guangdong, Guangxi, Yunnan, Hainan and the Red River drainage in northern Vietnam. At present, there are three recognized species in this genus: Cranoglanis bouderius, C. multiraditus and C. henrici, but there are still some arguments on the species validity of this genus. Multivariate morphometrics was conducted to clarify the confusion of species validity of the endemic Asian genus of Cranoglanis. 43 morphometric characters were measured for 66 specimens of the three Cranoglanis species from Zhujiang River drainage, Yuanjiang River and Hainan Island. Principle Component Analysis was used to study the inter-specific variations of the Cranoglanis species. The result indicated that there were no prominent differences among these three species. The Cranoglanis species in China is suggested as only one species, Cranoglanis bouderius.
The genus Coilia belongs to Engraulidae in Clupeiformes, and it is a group of small fishes inhabiting the coastal of Western Pacific. There are four species distributed in China: Coilia ectenes, C. mystus, C. grayii, and C. brachygnathus. Some of the Coilia species became endangered in recent years. We determined mitochondrial cytochrome b gene (980bp) for 147 individuals of the four Coilia species collected from the Yangtze River and the East and South Sea of China to study phylogeny and phylogeography of Coilia. Engraulis japonicus and E. encrasicolus were selected as outgroup taxa. The phylogenetic trees were constructed using MP, NJ, and Bayesian analysis methods. In this part main conclusions were as follows:
Our molecular data suggested that Coilia ectenes taihuensis and C. brachygnathus could not be recognized as valid species, and they should be special ecological groups of C. ectenes. Individuals of the two subspecies of C. mystus form two different clades respectively, but these two clades are distantly related. The result indicated that the two subspecies of C. mystus should be considered as valid species. C. mystus and C. jiulongjiangensis were suggested as name of these two species. In China there are four valid species of Coilia: C. ectenes, C. grayii, C. mystus and C. jiulongjiangensis.
Phylogenetic analyses with NJ, MP and Bayesian methods resulted in the same tree topology. Coilia ectenes was the sister group to C. grayii. Then they formed the sister group with C. mystus. The species C. jiulongjiangensis was basal in the trees. We presumed that C. jiulongjiangensis was the primitive species in the genus and the other three were specialized. The estimated divergence time revealed that separation of C. ectenes and C. grayii happened in the middle Pliocene.
A total of 57 haplotypes were found in population genetic analysis, including 3 haplotypes in 5 individuals of C. grayii, 9 in 9 individuals of C. mystus, 16 in 20 individuals of C. jiulongjiangensis, and 29 in 113 individuals of C. ectenes. The natural populations of these four anchovy fish species had a high level of genetic diversity respectively. However, genetic diversity of the populations of C. mystus and C. jiulongjiangensis was higher than that of C. grayii and C. ectenes.
C. ectenes, C. jiulongjiangensis, C. ectenes can form Star-like genealogy. Population expansion had been found in the C. ectenes, C. mystus and C. jiulongjiangensis. Frequent gene flow seemed to exist between the populations of C. ectenes. The lack of geographic isolation may cause hybridization between different ecological groups. The lakes beside the Changjiang River might be the refuge of C. ectenes during the glacial epochs.
Gene flow had been blocked in C. mystus and C. jiulongjiangensis for a long time. C. jiulongjiangensis was differentiated evidently. The influence such as different water temperature, salinity gradient might be the cause of speciation.|