| Summary: | 碩士 === 國立臺灣海洋大學 === 海洋生物研究所 === 100 === Hypnea is an economically important red algal genus for production of phycocolloids and is widely distributed in intertidal and subtidal zones of the tropical and subtropical regions. The genus comprises about 66 species around the world. The economical important of the genus is as food or owing to carrageenan in thallus cell walls that are recently harvested abundantly in the northwestern Indian Ocean. The taxonomy of Hypnea is complicated often due to variable morphologies within a species from different geographic areas. Fifty species of Hypnea were previously recorded from Taiwan, but some species share a similarity of the external morphology and it is difficult to separate them apart in the field. In this study, I used rbcL sequence analyses to delineate species. The results showed that there are 14 species of Hypnea occurring in Taiwan, including H. flexicaulis, Hypnea sp. 1, H. cf. cervicornis, H. flegelliformis, H. chordacea, H. nidulans, H. japonica, Hypnea sp. 2, H. cf. charoides, Hypnea sp. 3, Hypnea sp. 4, H. boergesenii, Hypnea sp. 5 and Hypnea sp. 6, respectively. Among the 14 species, H. flexicaulis and H. flegelliformis are newly recorded. The fourteen clades within Hypnea detected based on rbcL sequence analyses from Taiwan can be roughly separated three sections based on morphology of habit: 1) thalli are erect, consisting obvious main axis, including four species (H. flexicaulis, Hypnea cf. cervicornis, H. flegelliformis and H. chordacea), 2) thalli are in entangled tufts or in cushion-like mat, including three species (H. japonica, H. nidulans, and Hypnea sp. 2), 3) thalli are composed of several, erect main axes with spinous branches and slender or tapering tips, including six species (Hypnea sp. 3, Hypnea sp. 4, H. cf. charoides, H. boergesenii, Hypnea sp. 5 and Hypnea sp. 6).
The rbcL sequence analyses partly supported the three sections of J. Agardh in 1850's and Tanaka in 1940's based on external morphology/ thallus habit. In this study, I have sequenced two collections of H. cervicornis from the eastern and southern Taiwan, and both sequences are almost identical. The previous record of H. spinella remains in doubt. On the other hand, the previous record of H. pannosa might be wrong identification of H. nidulans. I also sequenced H. boergesenii from type locality, Keelung, and concluded that H. asiatica from Korea is a later synonym. Six uncertain species (Hypnea sp. 1~Hypnea sp. 6) might be new species and call for a future study. Among the fourteen species, H. cervicornis, H. flegelliformis and H. chordacea have been widely recorded around the world. The species diversity of Hypnea is shown to be the highest in southern Taiwan, including nine species (H. flexicaulis, Hypnea cf. cervicornis, H. chordacea, H. nidulans, Hypnea sp. 2, Hypnea cf. charoides, Hypnea sp. 3, Hypnea sp. 5 and H. boergesenii), whereas there are six species in the north (H. flexicaulis, H. flegelliformis H. chordacea, H. japonica and H. boergesenii). Five species are occurring in the east (Hypnea sp. 1, H. cf. cervicornis, H. cf. charoides, H. boergesenii and Hypnea sp. 6).
|
|---|
