| Summary: | 碩士 === 國立臺灣師範大學 === 生命科學研究所 === 97 === Rhododendron sect. Tsutsusi in Taiwan comprises of 10 species. These species are very similar morphologically and are all endemic except R. simsii. Many examples point out that rapid evolution and subsequent speciation are often occurred on newly formed island. The endemic feature of these species and the newly formed island feature of Taiwan suggest that Rhododendron sect. Tsutsusi in Taiwan may be a result of fast evolution. This study uses cpDNA matK and trnK intron sequences and nuclear DNA RPB2-i intron 2 and ITS sequences to investigate the phylogenetic relationship of these closely related species .
Phylogeny tree constructed by matK and trnK intron sequence shows three major groups; and which constructed by RPB2-i intron 2 sequence shows two major groups. The author discovers that RPB2-i sequences of all species have two copies except R. oldhamii, besides, different copies of
R. rubropilosum are separately grouped into two different groups. However, phylogenetic tree constructed by ITS sequences is not well resolved. From the results above, the highest genetic diversity of R. rubropilosum, and the comparison of coalescent time together, the author infers that R. rubropilosum is a hybrid origin.
Combine the phylogenetic results of cpDNA trnK-matK intron and low copy number RPB2-i intron 2 sequenses, Rhododendron sect. Tsutsusi in Taiwan can be classified into four groups: the first group comprises of R. simsii, R. longiperulatum,R. nakaharai,R. kanehirain, and
R. noriakianum; the second group comprises of
R. taiwanalpinum, R. breviperulatum; and R. lasiostylum; the third group comprises of R. oldhamii; and the last group comprises of R. rubropilosum. Phylogenetic relationship based on molecular data is coincident with the morphological treatment, except R. rubropilosum. Therefore, the results based on molecular data can unmask more inconspicuous information to infer the phylogenetic of Rhododendron sect. Tsutsusi in Taiwan.
Finally, based on the results, the author speculates there may be at least 3 independent origins of these closely related species. However, the author cannot ascertain that the speculation is accurate since the lack of samples of Rhododendron sect. Tsutsusi . Therefore, collecting more samples and using more sensitive markers in the future are necessary to study more about the origin and the divergence of Rhododendron sect. Tsutsusi in Taiwan.
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