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Polymorphic Microsatellite Loci in Two Freshwater Turtles and Genetic Diversity among Captive Breeding Stocks of Chinese Pond Turtle (Chinemys Reevesii)

Author: ZhangZuo
Tutor: ZhengRongQuan
School: Zhejiang Normal University
Course: Ecology
Keywords: Chinemys reevesii Mauremys mutica Microsatellite Enriched genomic library FIASCO Genetic diversity Genetic differentiation
CLC: S917.4
Type: Master's thesis
Year: 2010
Downloads: 103
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Abstract

Chinese Pond Turtle (Chinemys reevesii Gray,1831) is the most widely distributed turtle, it is also one of the main turtle species in China with commercial and medicinal importance. Even though the population of farmed C. reevesii increased in China, the wild population significantly declined in both numbers and distribution as a result of commercial over-exploitation and habitat destruction. Chinese Pond Turtle has been classified as endangered in the IUCN Red List of Threatened Species and Chinese Red List of Threatened Species. The Asian Yellow Pond Turtle (Mauremys mutica Cantor,1842) is distributed in China, Japan and Vietnam. In 2002, this species was listed in AppendixⅡof CITES and listed as endangered in the IUCN Red List of Threatened species because of overhunting and habitat destruction in the wild. Owing to the higher values for food and remedy than other species of turtle, it has become one of the most commonly reared and highly traded chelonians in Asian. Recently, its husbandry and management has been a focus of aquaculture practice.To provide effective conservation and management for these natural and captive populations, there is an urgent need to gain a better understanding of its population and genetic structure. Highly polymorphic microsatellite loci will provide a powerful molecular toolkit and the statistical power of analysis of population structure, molecular phylogeny and molecular-derived breeding data in these important freshwater turtle species. The results are as follows:1. Eight polymorphic microsatellite loci were isolated from the Chinese Pond Turtle (Chinemys reevesii Gray,1831). All loci are highly polymorphic, with seven to 17 alleles per locus (average= 10.88). Values of expected and observed heterozygosities ranged from 0.703 to 0.920 and 0.321 to 0.966, respectively. Three of eight loci (Cre9, Cre37, Cre46) showed significant departures from Hardy-Weinberg equilibrium. After sequential Bonferroni correction,we suggest such deviations from expectations may be due to the presence of null alleles (the frequency of null alleles of Cre9, Cre37, Cre46 are 0.1309,0.5163,0.6108, respectively) or the sampling strategy with individuals from structured populations. We did not detect any linkage disequilibrium between loci following sequential Bonferroni correction.2. Fourteen polymorphic microsatellite loci were isolated from the Asian Yellow Pond Turtle (Mauremys mutica Cantor,1842). The number of alleles per locus ranged from 5 to 15. Observed and expected heterozygosities ranged from 0.448 to 0.889 and 0.593 to 0.923, respectively. After sequential Bonferroni correction, 7 of the 14 loci (Mmu3, Mmu4, Mmu7, Mmu8, Mmu9, Mmu10 and Mmull) showed significant deviations from Hardy-Weinberg equilibrium (P<0.01). The use of MICROCHECKER indicated that this phenomenon may be the result of null alleles (0.032-0.243). No significant linkage disequilibrium was detected among the fourteen loci (P>0.05). This is the first set of microsatellite markers developed for this species so far, and these loci are independently evolving genetic markers and are useful for stock study and genetic analysis of M. mutica.3. In this study, eight highly variable microsatellite loci were used to investigate genetic diversity and stocks structure of Chinese pond turtle in China. In total, 130 alleles at the eight loci in the seven stocks were detected. The number of alleles per locus ranged from 9 to 26, average value of the polymorphic information content was 0.71, and the observed (Ho) and expected heterozygosity (HE) ranged from 0.30 to 0.87 and from 0.60 to 0.93, respectively. Five of the eight loci were deviation from Hardy-Weinberg equilibrium, which mostly due to deficits of heterozygote. AMOVA also revealed that the variation within individuals was 84.29%, whereas the variation among stocks explained only 5.91% of the total variance. Though Chinese pond turtle had high-level of genetic diversity and low-level of genetic differentiation, an obvious geographic variation pattern was still existed in sample areas. The dendrogram based on genetic distance showed two major clusters:the HBJZ stock alone was in one cluster, which is sampled from the north of Yangtze River. The cluster, therefore, was referred to as the northern China cluster. The other cluster, southern China cluster, consists of individuals from sampling localities distributed in the south of Yangtze River. The discovery of unique alleles within the stocks supported the conclusion that these stocks had differentiated from each other and that gene flow having been restricted among populations gradually. Thus, it may be possible to form a new superior broodstock with high genetic diversity by combining turtles from different stocks, and measures should be taken to prevent further erosion of genetic diversity.

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CLC: > Agricultural Sciences > Aquaculture, fisheries > Aquatic basic science > Aquatic Biology > Aquatic Zoology
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