A Biosystematic Study on Euphrasia L. (Scrophulariaceae) in Taiwan
Date Issued
2004
Date
2004
Author(s)
Wu, Ming-Jou
DOI
en-US
Abstract
Euphrasia plants are hemiparasitic herbs comprised of 170 species and they are distributed throughout the cold regions of the northern hemisphere, Australia and South America. They also inhabit in the alpine or subalpine areas of tropical or subtropical Southeast Asia. In Taiwan, the plants grow on mountains at elevations above 2000 m, and only rarely grow at elevations between 1000 and 2000 m. The habits of Euphrasia in Taiwan are mainly distributed widely throughout Sheipa, Taroko, and Yushan national park region. The controversial taxonomy of Euphrasia is mostly due to the overall similarity among species, and some morphological polymorphisms at intraspecific level. The plants vary in leaf size and shape, but the lower leaves usually are smaller, narrower and less dentate during their development, whereas the upper leaves are larger, wider, and more dentate. The size and growth rate of the plants are also influenced by whether they have established on hosts, as well as by the host species.
Four groups/taxa are demonstrated in both principle coordinates analysis (PCO) and the unweighted pair-group method using arithmetic averages (UPGMA) based on morphological data. The ovule number per ovary, ovary length, spot distribution patterns on lower lip of the corona, and ratio of flower width to length can be used to distinguish these taxa.
The chromosome number was n=11, and all four taxa were diploids. The diploids are primitive compared with previous reports of tetraploids in Europe, tetraploids, hexaploids and 10-14 ploids in Australia, and octaploids in South America. Their primitiveness corresponds with the primitive state in the perennial section, which might imply that Taiwanese Euphrasia are relics.
Examining 676 individuals in 24 populations detected four polymorphic allozymes for genetic variation. No discrimination of these allozymes in the species boundary was found using population aggregation analysis (PAA) and UPGMA.
In the study of nuclear ribosomal ITS sequences, one-third (48) of 147 individuals in 55 populations have nucleotide additivity. It implies that hybridization occurred among Taiwanese Euphrasia taxa. A phylogenetic tree was reconstructed using maximum parsimony method based on 14 haplotypes of 99 nonadditivity individuals along with Aeginetia indica L., Pedicularis verticillata L., and six foreign Euphrasia of Section Euphrasia. The phylogenetic tree shows that four taxa of Taiwanese Euphrasia are monophyletic. Three lineages shown on the phylogenetic tree were not congruent with four taxa of Taiwanese Euphrasia, but did correlate with geographic distribution of the plants. It is inferred that individuals among different taxa shared the same haplotype due to ancient polymorphisms.
Using the nested clade analysis (NCA), the history of population of Taiwanese Euphrasia is inferred based on nrITS sequences of 99 nonadditivity individuals in 40 populations. A nested cladogram that combined 14 haplotypes was designed to discern the relationship between gene genealogy and geographical distribution. NCA implies that the current genetic distribution arose from six past fragmentation events that occurred at different nesting levels as well as one instance each of long distance colonization and contiguous range expansion. The several past fragmentation events at various nesting levels implied that several refuges previously existed. From the NCA, we postulated the following scenario of the population history of Taiwanese Euphrasia. At the beginning of or just before the Pleistocene era, Euphrasia settled in the mountainous areas of Taiwan. During an early glacial degeneration, a fragmentation event that probably occupied different elevations separated Euphrasia plants into two groups. Thereafter, by a glacial invasion, the distribution range of Euphrasia expanded toward southward at horizontal and upward at elevation. Subsequent fragmentation occurred during other glacial degenerations, and the population contracted toward northward at horizontal and upward at elevation. Therefore, populations of Euphrasia plants isolated by mountainous habitat-islands might have arisen from the most recent fragmentation event.
Allozyme variation and nrITS evidence suggested that Taiwanese Euphrasia plants are probably conspecies. However, taxonomic treatment based solely on morphology as in the case of classification of Euphrasia treated by Yeo (1978), we remains the taxonomic treatment proposed by Wu & Huang (1998) unchanged. The four taxa are: E. nankotaizanensis Yamam., E. tarokoana Ohwi, E. transmorrisonensis Hayata, and E. transmorrisonensis Hayata var. durietziana (Ohwi) T. C. Huang & M. J. Wu.
Subjects
加成性核甘酸
碎雪草屬
玉山小米草
南湖碎雪草
太魯閣小米草
E. transmorrisonensis Hayata
E. transmorrisonensis Hayata var. durietziana T. C
E. tarokoana Ohwi
E. nankotaizanensis Yamam.
Euphrasia
Nucleotide additivity
SDGs
Type
other
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