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Systematics and Phytogeography |
2Department of System Sciences, Graduate School of Arts and Sciences, the University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902, Japan; 3Graduate School of Science and Technology, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan; 4Tsukuba Botanical Garden, National Science Museum, 4-1-1 Amakubo, Tsukuba 305-0005, Japan; 5Faculty of Life and Environmental Science, Shimane University, 1060 Nishikawatsu-cho, Matsue-shi, Shimane 690-8504, Japan; 6The University of the Air, 2-11 Wakaba, Mihama-ku, Chiba 261-8586, Japan; 7Graduate School of Science and Technology, 2-39-1 Kurokami, Kumamoto 860-8555, Japan; 8Department of Biology, Faculty of Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
ABSTRACT
Species complexes consisting of ill-defined "species" are widely known among ferns, and their involvement with reticulate evolution is expected. Nevertheless approaches to reticulation history with DNA markers are not yet commonly adopted. We have successfully elucidated the biological status of the Vandenboschia radicans complex in East Asian islands by combining analyses of ploidy level, a cpDNA marker (rbcL), and a nuclear DNA marker (GapCp). The results based on 266 individuals collected from 174 localities throughout Japan and Taiwan suggest that complicated hybridizations have occurred involving at least three parental diploid species from within the V. radicans complex and Vandenboschia liukiuensis, which was formerly considered to be distinct from this complex. Triploids are the most common cytotype, but they show no evidence of apogamous reproduction, while all nonhybrid diploids are rare and have very limited distribution. Possible accounts of this phenomenon will be briefly discussed including the possibility of relict distribution and occasional apogamous reproduction.
Key Words: GapCp hybrid Hymenophyllaceae Japan rbcL reticulate evolution single-strand conformation polymorphism (SSCP) Vandenboschia
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