Low Genetic Diversity of Cycas taitungensis (Cycadaceae), an Endemic Species in Taiwan, Revealed by Allozyme Analysis

本研究目的在利用同功酶技術以探討台東蘇鐵之族群遺傳結構。僅有二個台東蘇鐵族群現存於台灣東南部。所分析的19個酵素系統共有40個基因座，除Mdh-2（共有三個對偶基因）外其餘基因座均屬單型性。每基因座之對偶基因數目，鹿野溪與海岸山脈族群各1.08個與1.05個，平均l.07個。有效對偶基因數目極低，平均僅1.01個。多型性基因座百分比與其平均數均為2.5%。平均之異質性鹿野溪為0.014，而海岸山脈為0.011，平均為0.013。因此台東蘇鐵具有極低之遺傳變異。F值統計均呈負值，經X^2分析顯示Mdh-2在族群內之基因型分佈符合哈溫平衡定律。在族群間分化方面，F(下標 st)值為0.034，因此大部份(96%)之遺傳變異存在於族群之內，分化程度甚微。

關鍵字

台東蘇鐵；同功酶；遺傳變異

並列摘要

The purpose of this study was to investigate the population genetic structure of Cycas taitungensis C. F. Shen, K. D. Hill, C. H. Tsou & C. J. Chen using isozyme techniques. Only 2 isolated populations of C taitungensis were found in the southeastern part of Taiwan. Nineteen enzyme systems examined were encoded by 40 putative loci. All loci were monomorphic with the exception of Mdh-2, which was resolved into 3 alleles. The mean number of alleles per locus of these 2 populations, Luyei River and Coastal Range, was 1.08 vs. 1.05, with an average of 1.07. The mean effective number of alleles was considerably low, averaging 1.01 for both populations. The mean percentage of polymorphic loci and average value were both 2.5%. Mean heterozygosity was 0.014 for Luyei River and 0.011 for Coastal Range, with an average of 0.013. In conclusion, C taitungensis exhibits extremely low levels of genetic diversity. Wright's F-statistics showed negative values. The x^2 analyses revealed that the observed distribution of genotypes for Mdh-2 within population was in Hardy-Weinberg equilibrium. In terms of genetic differentiation among populations, the F1 value was 0.034; thus more than 96% of the genetic diversity resided within a population, and the genetic differentiation between populations was low.

並列關鍵字

Cycas taitungensis ； allozyme ； genetic variation

國際替代計量

Low Genetic Diversity of Cycas taitungensis (Cycadaceae), an Endemic Species in Taiwan, Revealed by Allozyme Analysis

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