Taxonomy of the Euphrasia transmorrisonensis (Orobanchaceae) complex in Taiwan based on nrITS
Species delineation in Euphrasia has long been a challenge for taxonomists. In this paper, DNA sequences are used to evaluate the morphological taxa of Taiwanese Euphrasia as well as to elucidate the phylogenetic relationship among them. ITS sequences of 147 samples of Euphrasia, one Aeginetia, and one Pedicularis from Taiwan along with nine samples of Euphrasia from abroad were studied. Six non-native species of Section Euphrasia were used as outgroups and 14 haplotypes from four taxa of Taiwanese Euphrasia , E. tarokoana Ohwi, E. nankotaizanensis Yamam., E. transmorrisonensis Hayata, and E. transmorrisonensis var. durietziana (Ohwi) T.C. Huang & M.J. Wu, served as the ingroup to reconstruct a phylogenetic tree according to the criterion of maximum parsimony. Based on the phylogenetic tree, three monophyletic haplotype lineages of the ingroup were obtained, closely correlating with geographical distributions (with some overlap in adjacent regions). However, plants of different taxa are found in the same lineage. Lineage I includes all four Taiwanese taxa, whereas lineage II includes two taxa, E. transmorrisonensis, and E. transmorrisonensis var. durietziana . Lineage III includes three taxa: E. nankotaizanensis , E. transmorrisonensis, and E. transmorrisonensis var. durietziana. Different taxa share a common haplotype. Euphrasia nankotaizanensis , E. transmorrisonensis , and E. transmorrisonensis var. durietziana share haplotype E; E. nankotaizanensis and E. transmorrisonensis share haplotype D; and E. transmorrisonensis and E. transmorrisonensis var. durietziana share haplotypes G and N. The shared haplotypes may reflect retained ancestral polymorphisms at a neutral locus (ITS) through a series of recent speciation events (lineage sorting). The nucleotide additivities are found frequently among taxa. For example, the A+B additivity pattern of E. tarokoana and E. transmorrisonensis var. durietziana could reflect hybridization. Nucleotide additivity also provided insight into reticulate relationships among populations within and between taxa. Lineage sorting and hybridization might be mechanisms driving speciation in Taiwanese Euphrasia, resulting in retention of morphology and adaptation to distinct habitats. According to ITS evidence, we reconfirm four taxa of Euphrasia in Taiwan.
Document Type: Research Article
Graduate Institute of Plant Biology, National Taiwan University, Section 4, Roosevelt Road, Taipei, 106, Taiwan and Department of Science Education, National Hualien Teachers College, Huahsi Road, Hualien, 970, Taiwan.
Graduate Institute of Plant Biology, National Taiwan University, Section 4, Roosevelt Road, Taipei, 106, Taiwan.
Publication date: November 1, 2004
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