天鹅洲迁地保护江豚群体的遗传评估与发展预测

GENETIC EVALUATION AND DEVELOPMENT PROGNOSIS ON EX SITU CONSERVED YANGTZE FINLESS PORPOISES LIVING IN TIAN-E-ZHOU NATIONAL NATURAL RESERVE

文章以2008年春季遭受严重雪灾的天鹅洲白鱀豚国家级自然保护区迁地保护江豚群体为研究对象,利用物种特异性微卫星遗传标记对该群体的遗传多样性进行了评估,并通过软件对其发展趋势进行了模拟和预测。研究结果表明,虽然2008年春季雪灾并未导致该群体遗传多样性的严重损失,灾后群体依然表现出中等水平的微卫星遗传多样性(18个座位的平均等位基因数为4.780,平均观察杂合度和期望杂合度分别为0.748和0.674);但模拟结果显示,该迁地保护江豚群体的遗传多样性将快速下降,100年后仅能保留约79%的等位基因和约84%的遗传杂合度。此外,模拟结果表明,通过增加群体数量和调整群体性比可有效减缓该群体遗传多样性的下降速度。根据研究结果,并结合长江江豚自然种群快速下降的现状,作者提出天鹅洲迁地保护江豚群体当前最重要的保护策略应该是尽早补充一定数量的、合适的野生个体,在加强遗传多样性保护的同时使其群体数量快速增长并形成一个更大规模的有效繁殖群体。

The Yangtze finless porpoise （Neophocaena phocaenoides asiaeorientalis） is a unique freshwater subspecies of Neophocaena phocaenoides, which is endemic to the Yangtze River of China and now is critically endangered. As one of the three possible effective conservation measures, an ex situ conservation breeding colony has been successfully established for the Yangtze finless porpoise in Tian-e-Zhou Baiji National Natural Reserve, located at Shishou City in Hubei Province. However, in the early spring of 2008, a large snowstorm, lasting several days, led to the death of sev- eral porpoises in the reserve. To estimate the genetic loss caused by the snowstorm, a batch of 18 species specific mi- crosatellite markers were employed to investigate the genetic diversity of the colony before and after the snowstorm respectively. Besides, the computer software BottleSimV2.6, was applied to simulate the losing process of genetic di- versity in the future. Results indicated that the Tian-e-Zhou ex situ conservation colony after the snowstorm still showed moderate level of genetic diversity （for 18 microsatellite loci, A=4.780, Ho=0.748, He=0.674）. The snowstorm in 2008 did not cause severe genetic loss. Nevertheless, simulation results showed that genetic diversity of the Tian-e-Zhou ex situ conservation colony would decline rapidly in the future, if no effective measures were taken. Approximate 79% of the alleles and 84% of the heterozygosity would be reserved after 100 years. Simulations also indicated that lose of ge- netic diversity would be slowed down by increasing the population size and optimizing the sex ratio. Combining the simulation results from this study and the fact of rapid decline in wild population, the best ex situ conservation strategy for Yangtze finless porpoises living in the Tian-e-Zhou National Natural Reserve is to recruit suitable individuals from other wild populations, to establish a larger, more effective breeding population, with much greater genetic diversity.