Population Genetic Structure And Conservation Genetics Of Common Pheasant (Phasianus Colchicus Strauchi) Based On Mitochondrial DNA Control Region Genes

Common pheasant(Phasianus colchicus)is a world-widely distributed species as one of the most important game birds with numerous subspecies,while in China, there are 19.Our study is to demonstrate genetic structure and conservation genetics of common pheasant Gansu subspecies(P.c.strauchi),which is an endemic resident of Gansu,Ningxia and Qinghai provinces in northwestern China.Mitochondrial DNA(mtDNA)genome has proven to be useful in many avian phylogenetic and population studies,and the control region(CR)plays an important role in replication and transcription in the mitochondrial(mt)genome.Its supposedly high rate of DNA substitution makes it a suitable marker for our study.In our study,a total of 132 samples from 10 populations of P.c.strauchi were collected from ten localities in Gansu,Ningxia and Qinghai provinces.We obtained those samples during three consecutive autumns 2005,2006 and 2007.The entire mtDNA control region genes were PCR amplified and sequenced directly.We used different softwares to calculate the genetic structure within and among P.c.strauchi populations.The aims of our study are:(1)to calculate the genetic diversity of common pheasant at a level of subspecies;to demonstrate the divergence variation and gene flows among P.c.strauchi populations in different habitats;(2)to reveal the population genetic structure of P.c.strauchi;(3)to reconstruct the phylogeographic structure of P.c. strauchi and to infer the impacts of environmental and climate change on its systematic evolutionary process;(4)to give support to the nascence-center hypothesis of pheasants;to infer the possible dispersal route in P.c.strauchi evolutionary history; (5)to compare the morphological variation and genetic diversity referred to descriptions of P.c.strauchi morphological characters;(6)to discuss the conservation status of P.c.strauchi as viewed from genetics.The results of our study are as below: The average nucleotide composition G+C=40.5%,which was typical for avian mitochondrial DNA control regions.A total of 50 variable sites defined 54 haplotypes. The most common haplotype was H1 with 26 individuals from 8 populations.The theory predicts that the most frequent and widespread haplotypes are ancestral.Based on this coalescent theory,it suggested that the haplotype H1 was ancestral.The average nucleotide diversity was at a low level(0.0031),while the average haplotype diversity was at a high level(0.9421).The value of Fst and value of Nm implied there was no,however,significant genetic divergence among populations mainly because populations lacking of spatial separation and communicating frequently.Fu's Fs test indicated that P.c.strauchi has suffered a rapid spatial expanding during its evolutionary history.Diverge time was suggested 0.08 Ma to 0.28 Ma by calculating genetic distance among populations.The results gave support to hypothesis that the nascence-center of pheasants was in Hengduan Mountain range in southwestern China,which indicated the possible dispersal route of P.c.strauchi was from southwest to northeast and northwest during its evolutionary history.A total of 54 haplotypes interweaved in the phylogenetic tree and did not cluster into separate branches according to separate sampling localities as imaged.The phylogeographic structure of P.c.strauchi belonged to "phylogenetic continuity,lack of spatial separation".Due to the maternal inheritance of mitochondrial DNA while paternal inheritance of morphologic characters such as white eyebrow and white collar,it didn't show strict congruence between genetic differentiation and morphologic variation.For the sake of decreasing impacts coming from both habitat fragmentation and human behavior to P.c.strauchi,we should give first protection priority to Chengxian(CX)and Datong(DT) populations which had high genetic diversity and to Zhangxian(ZX)population which had been isolated sharply.