| Summary: | 碩士 === 國立東華大學 === 自然資源與環境學系 === 100 === Plants of Euphrasia, eyebrights, are annual or perennial hemiparasitic herbs. There are about 170 species in the world. The genus distribution is mainly in temperate zones of the northern hemisphere, Australia, South America, and in the alpine or sub-alpine areas of tropical or subtropical Southeast Asia. Though several studies have investigated the patters of dipolar disjunction and origins of Euphrasia, there are no conculusions argument, clarifying phylogenetic relationships between populations and processes of migration. These remain challenging issues to be resolved. In this study, sequences of the trnD-trnT non-coding spacer of chloroplast DNA, G3pdh (glycerolehyde – 3 – phosphate dehydrogenase) gene, and AAT (Aspartate aminot- ransaminase) gene of the nuclear DNA were used to investigate the phylogeographic patterns of Euphrasia in Taiwan, the Philippines, Borneo, Papua New Guinea, Japan, Denmark, Chile, Australia and New Zealand. Low levels of nucleotide diversity (π) and haplotype diversity (h) detected in the three genes suggests that Euphrasia in Taiwan and Borneo may have been affected by a bottle neck effect during their evolution. Tajima’s D tests in chloroplast DNA and G3pdh seqeances show that Euphrasia population signifiganly reduced by natural selection effects. These molecular markers cannot distinguish Taiwan morphological taxa. There is a high level of genetic differentiation between the taxa of Taiwan and the Philippines.
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