The Yellow Schizopygopsis Fish Genetic Diversity

The vast Qinghai-Tibetan Plateau, being renowned as"The Roof of the World", is the World's highest unique ecosystem. This region, along with southeast China, the Himalayan biodiversity hotspot, has been designated as one of World's 34 most important centers of biodiversity, because of it high species richness and abundance of endemic species. Schizopygopsis pylzovi, a member of the genus Schizopygopsis, is a Qinghai-Tibetan Plateau endemic fresh water fish species that is mainly distributed in the Qaidam drainages and the upper reaches of Yellow River in the northern and northeastern Qinghai-Tibetan Plateau. As one of the important natural fishery resourse, the Schizopygopsis pylzovi plays significant roles in the trophic web of plateau freshwater communities, and tolerates high hypoxia and low temperature, and shows highly adaptive to the peculiar ecological condition of the region, which gives it an abvious biological interest. So far, however, little is known about the genetic diversity, radiation and population structure. In the present study, the chromosome karyotype of Schizoygopsis pylzovi was studied by method of PHA—Colchicine injection in vivo. The result showed that the diploid chromosome number of Schizoygopsis pylzovi was 92, and it's karyotype formula was 24m+24sm+22st+22t, and NF=140. It was considered that Schizoygopsis pylzovi were likely to be diploidized from tetraploid, and possibly originated from one of the primitive Barbinae fishes.The lactate dehydrogenase isozymes were investigated in such organs as gill, liver, sexual gland, heart, swim bladder, kidney, eyeball, brain, muscle and serum of Schizopygopsis pylzovi in the Yellow River by means of polyacrylamide gel electrophoresis. The results showed that the lactate dehydrogenase isozymes were different in organs, which were highly correlative with adaptation of Schizopygopsis pylzovi to the hypoxia environment of Qinghai-Tibetan Plateau, and suggested that Schizoygopsis pylzovi were likely to be diploidized from tetraploid, and possibly originated from one of the primitive Barbinae fishes.In the present study, five populations (n=99) were collected from the Qaidam drainages and the upper reaches of Yellow River. Among the aligned sequences of 821 bp of the mitochondrial control region (D-loop), 77 (9.37%) nucleotide sites were variable, and a total of 53 haplotypes were identified. Of 53 haplotypes, only one haplotype (DT12) was shared by two populations from the upper reaches of Yellow River. Haplotype diversity (h=0.79±0.06) and nucleotide diversity (π=0.0027±0.0017) of population from Qiadam drainages lower than that of the populations from the upper reaches of Yellow River. The AMOVA analysis indicated that the genetic variation mainly occurred within populations instead of between populations. Both the pairwise Fst values and average pairwise difference supported significant population subdivision among populations, although no geographic clustering was observed. The most possible explanation of this result might be referred to the geographic barriers among drainages resulted from the recent uplift of Qinghai-Tibetan Plateau. The unimodal mismatch distribution of haplotypes, and selective neutrality test of Tajima's D (-1.497, P =0.058) and Fu's Fs (-24.741, P=0.001)all suggested that there might be a recent population expansion for Schizopygopsis pylzovi during the course of uplift of the Qinghai-Tibetan Plateau.