| Summary: | 碩士 === 國立師範大學 === 生物學研究所 === 83 === Electrophoretically demonstrable diversity of 15 enzymes encoded
by a total of 23 structural loci was analyzed in 22 sexually
mature populations of Alnus formosana(Burk.) Makino (Betulaceae)
in Taiwan. On average, 46.2% of the loci per population were
polymorphic, with a mean of 1.8 alleles per locus. The observed
heterozygosity was not significantly different from expected
heterozygosity(Ho=0.181,He=0.175). Approximately 98% of the total
genetic diversity resided within populations. Genetic distance
between populations waslow, ranging from 0 to 0.019 with a mean
of 0.004. F-statistics showed very low differentiation between
populations (Fst=0.038). Inbreeding coefficient (Fis=-0.057)
revealed that non-assortative mating was common in this species.
Most populations however, appeared homogeneous, implying that
high level of gene flow occurred among populations them. On the
other hand, heterogeneity of allele frequencies among populations
along elevational gradient was noted at seven loci. The finding
that significant correlations between allelic frequences and
elevational gradient revealed at SOD and PGM-1 loci suggest that
genetic variation tends to be partially corresponded with
temperature changes. Low genetic differentiation among popula-
tions in Formosan alder may be attributed to the factors such as
mating system, pollen and seed dispersal. Differential selection
pressures and life-history seemed to be the main factors that
maintaining theobserved genetic variability of this species.
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