The phylogeographical study of Castanopsis carlesii Hayata
Date Issued
2006
Date
2006
Author(s)
Cheng, Yu-Pin
DOI
zh-TW
Abstract
The noncoding region sequence of cpDNA and the allozyme marker were used to conduct the phylogeographical study of Castanopsis carlesii, a subtropical and temperate tree species in Taiwan. C. carlesii, belonging to the Fagaceae, is one of the most common and dominant tree species which adapt to the subtropical and tempetate climate in Taiwan.
In this study, we examined spatial patterns of chloroplast DNA (cpDNA) variation in a total of 30 populations of C. carlesii, including 201 individuals sampled throughout Taiwan. By sequencing two cpDNA fragments using universal primers (the trnL intron and the trnV-trnM intergenic spacer), we found a total of 1663 bp and 21 polymorphic sites. These gave rise to a total of 28 cpDNA haplotypes. The level of differentiation among the populations studied was relatively high (GST = 0.723). Two ancestral haplotypes are widely distributed. The Central Mountain Ridge (CMR) of Taiwan represents an insurmountable barrier to the east-west gene flow of C. carlesii. Among the populations studied, three separated populations, at Lienhuachih, Fushan and Lichia, have high nucleotide diversity. Estimates of NST - GST for populations on both sides of the CMR indicate that no phylogeographical structure exists. According to the genealogical tree, number of rare haplotype and population genetic divergence, this study suggests that two potential refugia existed during the last glaciation: the first refugium was located in a region to the north of Hsuehshan Range (HR) and west of the CMR; the second refugium was located in south, especially southeastern Taiwan. In fact, the second refugium happens to be the same as that reported for Cyclobalanopsis glauca. A “Star-like” genealogy is characteristic when all haplotypes rapidly coalesce and is a general outcome of population expansion. The neutrality test and mismatch distribution also suggest demographic expansion.
Using genetic parameters to determine the heterozygosity and the mean FST value of each population, we inferred the evolutionary history of Castanopsis carlesii in Taiwan. In this study, 22 populations of C. carlesii throughout the island were sampled covering an elevational range of 50~2300 m. Starch gel electrophoresis was used to assay allozyme variations, and 11 loci from nine enzyme systems were detected. 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. From the data of expected heterozygosity, one major diversity center was situated in central Taiwan corroborating previous reports for other plant species. According to the mean FST value of each population against the remaining populations, the most-divergent populations were situated in two places. One includes the populations of Anmashan, Fushan, and Tungao, and is located in north-central Taiwan between 24.80°N and 24.20°N. The other is located in southeastern Taiwan between 22.40°N and 23.10°N, and includes the populations of Hsinkangshan, Tona, and Tawu. These two regions are approximately convergent with the most divergent locations determined for several other plant species using chloroplastic DNA markers. In conclusion, the result of genetic differentiation study obtained from isozymes agrees well with that from chloroplastic DNA markers.
Subjects
親緣地理學
長尾栲
殼斗科
Phylogeography
Castanopsis carlesii
Fagaceae
Type
other
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