[SSR polymorphism of Alligator sinesis and conservation strategy of genetic diversity]

Chinese alligator, Alligator sinesis, is a critically endangered endemic species under legislative protection. Results of recent investigations revealed that the number of the alligator was continuously declining in the past 50 years and less than 150 individuals were surviving in the wild until 2000. In order to prevent the extinguishing of this species, the Reproductive Research Center of Alligator sinesis and the National Nature Reserve of Alligator sinesis were set up in early 1980s in Xuanzhou, Anhui Province. After 20 years of breeding efforts, the number of captive individuals has been brought up to more than 10,000 in total. In order to reveal the genetic structure of Chinese alligator population, total of 39 individuals including 7 wild individuals outside of the research center were sampled to construct wild, F1 and F2 groups according to their generations, and 10 micorsatellite loci selected from 25 primer pairs originally designed for Alligator mississippiensis were employed for investigating the genetic diversity of Alligator sinesis. The results indicated that, contrasting with Alligator mississippiensis and some other endangered species, Chinese alligator had an extremely low genetic diversity level with A = 2.38, Ne = 1.60, Ho = 0.374, He = 0.350 and PIC = 0.327. There were no significant differences of A, Ne, Ho, He, PIC and each SSR locus alleles frequency distribution among 3 groups. However, Hardy-Weinberg equilibrium analysis revealed that F2 captive group showed a remarkable genetic disequilibrium at loci Ami-mu-6 and Ami-mu-222. The reason accounting for the current genetic status of Chinese alligator is dramatically shrink of the population in past decades. Due to the lack of significant difference between wild group and captive group, all survived Chinese alligator should be treated as one ESU in the next conservation practice. More attention regarding the effective population size and low frequency alleles should be emphasized in genetic management of captive alligators and establishing new separate propagation.