Allozyme Variations of a Widespread Tree Fern, Alsophila spinulosa (Hook.) Tryon (Cyatheaceae), in Taiwan

Abstract

Allozymes were used to detect the genetic diversity of Alsophila spinulosa, a widespread tree fern in Taiwan. Allozyme polymorphisms of 6 enzyme systems, including 9 loci and 12 alleles, were used to estimate the genetic diversity of A. spinulosa from 9 sites throughout Taiwan. The mean number of allele per locus (A) was 1.34, the percentage of polymorphic loci (P) was 34.5%, the observed heterozygosity (H(subscript o)) was 0.145, and the expected heterozygosity (H(subscript e)) was 0.141. The genetic diversity of A. spinulosa in Taiwan was higher than mean values of other diploid ferns and tree ferns. The large population size and an intergametophytic outcrossing mating system were thought to be important factors in A. spinulosa maintaining a higher level of genetic diversity. Inbreeding has also sometimes occurred, and this might have assisted the successful colonization by a single long-distance dispersal spore. At the population level, the Nanjenshan population (NJ), located in southern Taiwan, showed the highest expected heterozygosity (H(subscript e)). Additionally, lower levels of genetic differentiation among populations were detected and are thought to be a result of high gene flow due to spores.