碩士 / 國立臺灣海洋大學 / 水產養殖學系 / 97 / This study aimed at investigating three conservation issues on Formosa landlocked salmon: (i) the phylogenetic relationship between Formosa landlocked salmon and other subspecies of Masu salmon complex (Oncorhynchus masou complex), (ii) the genetic diversity that exists in Formosa landlocked salmon, and (iii) the estimation of the sex ratio of Formosa landlocked salmon.
The phylogenetic tree is reconstructed based on AFLP data and by using neighbor-joining method and Nei's genetic distance. In this tree, Biwa salmon (O. m. subsp.) and Amago salmon (O. m. ishikawae) are clustered first, Masu salmon (O. m. masou) are clustered second, and finally Formosa landlocked salmon (O. m. formosanus) are jointed to this cluster. The high bootstrap values at each node indicate that this tree is robust. The results show that instead of dividing from Msau salmon, Formosa landlocked salmon is the first subspecies divided from ancestor of Masu salmon complex. Formosa landlocked salmon is considered as an evolutionarily significant unit (ESU) due to geographic separation and genetic differentiation among Masu salmon complex. Furthermore, several subspecies specific bands, which are helpful for distinguishing subspecies from each other, are found in each member of Masu salmon complex.
Genetic diversity of Formosa landlocked salmon in Chichiawan Stream are examined by using AFLP and Microsatellite markers. For consecutive two years (2004 and 2005), a total of fifty-eight individuals (thirty in 2004 and twenty-eight in 2005) were examined. Of twenty-seven Microsatellite loci, only one locus was polymorphic with two alleles while others were monomorphic. The average He are 0.0071 and 0.0067, respectively. One hundred and ninety six loci were detected using three AFLP selective primer pairs, of which fifty-eight were polymorphic with a proportion of 29.59%. The average He are 0.0045 and 0.054, respectively. Both Microsatellite and AFLP data show the low genetic diversity in Formosa landlocked salmon. Comparison of allele frequency of fifty-eight AFLP polymorphic loci between two years, eighteen (about one third) of the amplified polymorphic loci became fixed (p = 100%) or lost (p = 0%) and another sixteen (about one third) was changed in the 2005 population. The results indicate that Formosa landlocked salmon are losing genetic diversity due to genetic drift.
In this study, a simple, reliable, non-invasive PCR method is developed to identify sex of Formosa landlocked salmon. The reliability of sex identification is 98.40% (1.60% mismatch; two mismatches in 125 individuals) for Formosa landlocked salmon. The sex ratios (male/female) of field Formosa landlocked salmon from 2004 to 2008 were 0.59, 0.50, 1.19, 0.57 and 0.72, respectively. The sex ratio of 2007 was significant differed from 1:1 (p<0.05). The results indicate the sex ratio of Formosa landlocked salmon is not consistent with 1:1. Biased sex ratio has to be considered when effective population size is counted.
In summary, Formosa landlocked salmon is an ESU of Masu salmon complex and should be conserved. In conservation program, AFLP and sex marker are useful tools for genetic management and conserving maximum genetic diversity.
| Identifer | oai:union.ndltd.org:TW/097NTOU5086019 |
| Date | January 2009 |
| Creators | Te-Hua Hsu, 徐德華 |
| Contributors | Jin-Chywan Gwo, 郭金泉 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 91 |
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