LOW GENETIC-VARIATION IN AMENTOTAXUS-FORMOSANA LI REVEALED BY ISOZYMEANALYSIS AND RANDOM AMPLIFIED POLYMORPHIC DNA MARKERS

The objective of this research was to use random amplified polymorphic DNA (RAPD) and isozyme analysis to investigate genetic variation in n arrowly distributed populations of Amentotaxus formosana Li. A total o f 20 loci from 10 enzyme systems were analysed in 50 individual trees from each of the two natural populations. No isozyme variation was obs erved in the Tsatsayalai population. Phosphoglucose isomerase (Pgi-1) was the only polymorphic enzyme in the Tawu population, giving 5 per c ent polymorphic loci with 0.008 expected heterozygosity. No genetic di stance was found between these two populations using isozymes. Amentot axus formosana demonstrated a high proportion of monomorphic RAPD frag ments, about 79 per cent, for 20 arbitrary oligonucleotide primers. Hi gh similarity (0.994) was found between the Tawu and Tsatsayalai popul ations. RAPD markers provided further confirmation of the low levels o f genetic variation in A. formosana detected by isozyme analysis. The value of isozyme analysis was emphasized by the finding of the rare al lele, Pgi-1a, which was present only in the Tawu population. Based on the analysis of 110 individuals, representing 16 per cent of a native population, it was found that the younger tree category had a higher f requency of Pgi-1a (0.125) than the older tree category (0.053), resul ting in an expected heterozygosity of 0.250 and 0.105, respectively. I t was inferred that the appearance of the Pgi-1a allele could be the r esult of a mutation in the Tawu population and that selection is actin g directly upon trees carrying this allele.