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Newsletter ‐ Asian conservation ecology
Yakushima Island
Yakushima is the 10th largest island (500 km2) of Japan, locating at 60 km away from the south end of mainland Kyushu. The island has many mountains as high as 1936 m. The large temperature gradient along the elevation and the enormous amount of precipitation (up to 10,000 mm per year) accommodates a unique set of flora and fauna. Some part of the island is a Natural World Heritage Site since 1993. Our GCOE program focuses this island as one of the core study sites. In this News Letter, we introduce two ongoing studies about freshwater fish and a unique parasitic plant, Mitrastema yamamotoi. (Right photos:
Nagata-dake, the second highest mountain in Yakushima and coast landscape near Kurio. Yusuke Onoda)
Freshwater Fishes in Yakushima Island
Yuichi Kano As Yakushima Island is far isolated from the mainland of Japan, only two genuine freshwater fishes are distributed; "Dojou" (Misgurnus anguillicaudatus) and "Medaka" (Oryzias latipes). However, there is a concern that the two species have been already extinct from the island. We did extensive survey more than a week (21-29 April 2010) to look for these two fish species, but we could not find any. Local peoples also said that they haven’t seen these two fishes at all recently,
while there existed much of them in the island until 30 years ago. This drop in population or, more likely, local extinction of these fish species may be related to the agrichemical and farm land Newsletter (Asian Conservation Ecology) Vol.2, No.3 (June 2010)
"Unagi" Anguilla japonica
"Oounagi" Anguilla marmorata
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Newsletter ‐ Asian conservation ecology consolidation.
On the other hand, many anadromous fishes (live in the ocean mostly, and breed in fresh water) can be seen in the island, such as Anguilla japonica, Anguilla marmorata, Tridentiger kuroiwae, Rhinogobius sp. and Sicyopterus japonicus. Of these fishes, Sicyopterus japonicus (Bouzuhaze) seemed to be particularly interesting. There are many high falls in Yakushima Island, some of which are over 50 m. Local people witnessed the Bouzuhaze to climb up these falls and distributed the upper side of the fall. If this is true, it is very exciting to clarify such unusual ability and its ecological significance.
A Colorless but Colorful Character in
forest floor
- Mitrastema yamamotoi
Lina Kawaguchi In Yakushima Island, there remain large populations of plant species that are rare or endangered in other parts of Japanese islands. Mitrastema yamamotoi (Mitrastemonaceae), a monoecious root holoparasitic plant parasitizing Castanopsis, is a typical example of such plant species. M. yamamotoi is distributed from Japan to Papua New Guinea. In Japan, it is distributed from Tokushima to Ryukyu Islands. This plant often forms large populations in low-altitude evergreen broadleaf forests in Yakushima Island although only a few small populations are found in other habitats in Japan.
Mitrastemonaceae is an evolutionary distinct group that has only two species in one genus (M. yamamotoi and M. matudae) and shows a unique morphology (see below photo). M. yamamotoi
"Bouzuhaze" Sicyopterus japonicus
Fall of "Ohko"
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Newsletter ‐ Asian conservation ecology
produces pinky-white, hard, waxy flowers that protrude 30-40 mm from the forest floor. Each flower protrudes above a series of decussate scale leaves at the base of short, fleshy, unbranched stem. The stamens and filaments are connate and form a conical body over the stigma and ovary. Belt-like anthers surround the upper part of the conical body. Flowers are in male stage at the beginning of blooming, and move to female stage when the conical body falls out. A large amount of nectar (up to hundreds of microliters) is accumulated in scale leaves. Despite this unique morphology, there is still much to be studied about the reproductive biology of M. yamamotoi. Most of the observations of pollinators have been episodic and seed-disperser has been almost unknown. We aim to clarify pollination and seed-dispersal systems of M. yamamotoi and how the unique morphology helps its reproduction. We have started observations of pollinators and seed dispersers using video recording and 10-sec interval photographs in Yakushima Island since last winter. As a result, we found a variety of previous unknown visitors to M. yamamotoi. We are planning to conduct more detailed research on whether and how such visitors contribute to the reproductive processes of this plant.
We hope to appeal to the public for the importance of biological interactions (e.g., host-parasite, plant-pollinator, and plant-seed disperser) in Yakushima Island by revealing the life history of this attractive and rare plant species.
Recent major activities
• Yakushima fish field course (21-29 April 2010, Yakushima)
• Tai-hu fish and aquatic plant field course (24 May- 1 June 2010, Tai-hu, China)
International Seminar Series
Lawrence D. Harder（University of Calgary,
Canada）
Machiavellian flowers: power and control in plant reproduction
12 May 2010
