Allozyme Variation of Populations of Castanopsis carlesii (Fagaceae) Revealing the Diversity Centres and Areas of the Greatest Divergence in Taiwan

Abstract

The genetic variation and divergence estimated by allozyme analysis were used to reveal the evolutionary history of Castanopsis carlesii in Taiwan. Two major questions were discussed concerning evolutionary issues: where are the diversity centres, and where are the most genetically divergent sites in Taiwan? Twenty-two populations of C. carlesii were sampled throughout Taiwan. Starch gel electrophoresis was used to assay allozyme variation. Genetic parameters and mean FST values of each population were analysed using the BIOSYS-2 program. Mean F(ST) values of each population against the remaining populations, considered as genetic divergence, were estimated using the FSTAT program. Average values of genetic parameters describing the within-population variation, the average number of alleles per locus (A=2.5), the effective number of alleles per locus (Ae=1.38), the allelic richness (Ar=2.38), the percentage of polymorphic loci (P=69%), and the expected heterozygosity (He=0.270) were estimated. High levels of genetic diversity were found for C. carlesii compared with other local plant species. Genetic differentiation between populations was generally low. From the data of expected heterozygosity, one major diversity centre was situated in central Taiwan corroborating previous reports for other plant species. According to the mean FST value of each population, the most divergent populations were situated in two places. One includes populations located in north central Taiwan between 24.80 degrees N and 24.20 degrees N. The other is located in south-eastern Taiwan between 22.40 degrees N and 23.10 degrees N. These two regions are approximately convergent with the most divergent locations determined for several other plant species using chloroplast DNA markers published previously. An important finding obtained from this study is that unordered markers like allozymes can be used to infer past population histories as well as chloroplast DNA markers do.