The phylogeography of the genus Taiwania
Date Issued
2009
Date
2009
Author(s)
Chou, Yen-Wei
Abstract
Taiwania is one of the Tertiary relic gymnosperms like the well-known Sequoia and Metasequoia. Fossil and pollen record evidence indicated that it was once widespread in the temperate region of Eurasia and even in North America but now only disperses in Taiwan, Southern China, northern Myanmar and northern Vietnam. Because the living populations of Taiwania have a scattered distribution pattern in Asia, these scattered populations may indicate information about the southward dispersal of Asian plants in the Tertiary, the dispersal of plants to Taiwan during the Quaternary glacial periods, and the formation of glacial refugia in Asia. However, although previous studies had analyzed the morphological and genetic variation among Taiwania populations scattered in Asia, no extensive phylogeographic study has ever been conducted to these surviving populations until now. In this study, five cpDNA regions (petG-trnP, trnH-psbA, trnV-trnM, trnC-ycf6 and trnL-trnF) were sequenced to analyze the genetic variation among Taiwania populations in Taiwan, China and a recently discovered population in Vietnam. Only eight haplotypes were distinguished, implying low genetic variations in all extant Taiwania populations. All Taiwanese populations consist only one haplotype, which is absent in the SE Asiatic mainland (Chinese and Vietnamese) populations. The haplotype network also revealed an eight-mutational-step difference between the Taiwanese haplotype A and the Asiatic mainland haplotype B, suggesting a strong genetic differentiation between Taiwania populations in Taiwan and in the SE Asiatic mainland. In contrast, the results of pairwise FST, Nm, and AMOVA implied a closer relationship between the Chinese and Vietnamese populations. The results of divergent time estimation suggest that the average differentiation time between the populations in Taiwan and the SE Asiatic mainland was ca. 1.9-2.5 mya, which was during the late Pliocene. Results in this study suggest a large differentiation between the remnants of Taiwania in Taiwan and in the SE Asiatic mainland, in which the two distinct haplotype lineages preserved in Taiwan and in the SE Asiatic mainland were probably diverged before the dispersal of ancient Taiwania populations to Taiwan. The distribution pattern of cpDNA haplotypes in living Taiwania populations may even suggest that the two haplotype lineages found in Taiwan and in the SE Asiatic mainland have two distinct origins. The scattered distribution pattern and the cpDNA variation of living Taiwania populations in Asia may be the result of fragmentation and retreat into several refugia, which was happened after the end of Quaternary glacial cycles.
Subjects
Taiwania
Tertiary relic gymnosperms
glacial refugia
divergent time
File(s)![Thumbnail Image]()
Loading...
Name
ntu-98-R95B44001-1.pdf
Size
23.32 KB
Format
Adobe PDF
Checksum
(MD5):9da28e903b47d524eaf9a95d2616d619