Molecular phylogeny of Sinocyclocheilus (Cypriniformes: Cyprinidae) inferred from mitochondrial DNA sequences.

More than 10 species within the freshwater fish genus Sinoncyclocheilus adapt to caves and show different degrees of degeneration of eyes and pigmentation. Therefore, this genus can be useful for studying evolutionary developmental mechanisms, role of natural selection and adaptation in cave animals. To better understand these processes, it is indispensable to have background knowledge about phylogenetic relationships of surface and cave species within this genus. To investigate phylogenetic relationships among species within this genus, we determined nucleotide sequences of complete mitochondrial cytochrome b gene (1140 bp) and partial ND4 gene (1032 bp) of 31 recognized ingroup species and one outgroup species Barbodes laticeps. Phylogenetic trees were reconstructed using maximum parsimony, Bayesian, and maximum likelihood analyses. Our phylogenetic results showed that all species except for two surface species S. jii and S. macrolepis clustered as five major monophyletic clades (I, II, III, IV, and V) with strong supports. S. jii was the most basal species in all analyses, but the position of S. macrolepis was not resolved. The cave species were polyphyletic and occurred in these five major clades. Our results indicate that adaptation to cave environments has occurred multiple times during the evolutionary history of Sinocyclocheilus. The branching orders among the clades I, II, III, and IV were not resolved, and this might be due to early rapid radiation in Sinocyclocheilus. All species distributed in Yunnan except for S. rhinocerous and S. hyalinus formed a strongly supported monophyletic group (clade V), probably reflecting their common origins. This result suggested that the diversification of Sinocyclocheilus in Yunnan may correlate with the uplifting of Yunnan Plateau.

[Genetic polymorphism of mitochondrial DNA in coding region in 16 ethnic populations of Yunnan].

The genetic polymorphism of mitochondrial DNA in the coding region in 16 ethnic populations of Yunnan was analyzed using PCR-RFLP in a total of 654 samples. Seventeen haplogroups were found, four of which were undefined haplogroups. Haplogroup distribution and Principal Component (PC) analysis showed that the ethnic groups descended from Bai-Yue tribe have B, F and M7 as the predominant haplogroups,which indicated their origination from southern China. Haplogroup A, D and N9 were predominant in the Mongolian ethnic group, reflecting their north-originated characteristics. The groups descended from Di-Qiang tribe shared the predominant haplogroups with both the south and north originated groups,which demonstrated that they inherit the maternal characteristics from both southern and northern populations. There is genetic difference among the populations in the same ethnic group and is usually smaller than that among the ethnic groups from different ancient tribes, but not necessarily smaller than that among the groups from the same tribe.

[Principal component analysis of Y-chromosome haplotype distribution in 18 ethnic groups in Yunnan Province].

Based on the historical records, 18 of the 26 ethnic groups in Yunnan Province are the descendant populations of three ancient tribes, Bai-Yue, Bai-Pu and Di-Qiang, linguistically belonging to the Daic, Austro-Asiatic and Tibeto-Burman, respectively. In order to trace the origins of these native ethnic groups, a total of 13 East Asian specific Y-chromosome biallelic markers were used to study the genetic structure of 20 local populations covering all the 18 ethnic groups in Yunnan Province. Haplotypes were analysis by PCR-RFLP method. Our results showed that H11 and H12 were the predominant haplotypes in the descendant populations of Bai-Yue tribe. H5, H6 and H8 were the dominant haplotypes in Di-Qiang descendants, and the frequencies of H6, H8 and H11 were very high in the descendant populations of Bai-Pu. To investigate relationships among 20 populations, a three dimensional PC analysis were performed based on the distribution of the 13 haplotypes. All populations were divided into two clusters in the PC plot. The first cluster was mainly composed by the descendant populations of Bai-Yue, and the second one was mainly composed by the descendants of Di-Qiang tribe. This result indicated that Bai-Yue and Di-Qiang's paternal lineage had different origins, which was in agreement with the historical documents and linguistic classification.

[The genetic evidence for sympatric speciation pattern of Cyprinus from Erhai Lake].

In the present paper, mtDNA RFLP and mtDNA D-loop sequencing were investigated in three species of Cyprinus from Erhai Lake. The results indicated that two mtDNA haplotypes were identified in three species of Cyprinus from Erhai Lake by using 16 restriction endonucleases. All individuals share the dominant type I except one individual of C. longipectoralis shows type II just with only one cleavage site polymorphism when tested by Dra I. Compared to the reported interspecific and intraspecific sequence divergence in fishes, the present divergence values of 0% - 0.0075% from the Cyprinus species native to Erhai Lake were too much lower. Furthermore, 449 bp of mtDNA D-loop region sequencing was investigated in these three Cyprinus species. There were six mtDNA haplotypes indicated by seven variation sites. The interspecific sequence divergence were 0.082% - 0.171%. It is also at least one degree lower than some allopatric Cyprinus species we studied. A remarkably low level of genetic divergence detected among the three species of Cyprinus species in Erhai Lake both by mtDNA RFLP and D-loop region sequencing provides direct genetic evidence for its sympatric speciation pattern, which could occurred without progressive adaptive genetic variation.