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南大東島は, 琉球列島の沖縄島から360km 東に浮かぶ海洋島である。南大東島において2017 年4 月, 7 月, 9 月にオオハマボウHibiscus tiliaceus ( アオイ科) の訪花動物相調査を実施したところ, シロオビキホリハナバチLithurgus collaris が頻繁に訪花するのが観察された. シロオビキホリハナバチはハキリバチ科の穿坑性種で, 中国, 日本 ( 本州• 九州), 台湾に至る広い分布域を持つ. 琉球列島では中琉球と南琉球に分布することが知られていたが, 南大東島では初めての記録である., Minamidaito-jima Island is an oceanic island located about 360 km east of Okinawa Island, in the Ryukyu Archipelago, Japan. We conducted observational surveys on flower visitors of Hibiscus tiliaceus (Malvaceae) on Minamidaito-jima Island in April, July and September 2017. Lithurgus collaris (Megachilidae) was found visiting the flowers of H. tiliaceus frequently. Lithurgus collaris is a wood-boring bee, and is widely distributed from China, Japan (Honshu and Kyushu) to Taiwan. Although L. collaris has also been known to be distributed in the central and southern Ryukyus, this is the first record of this species from Minamidaito-jima Island., 論文

The buff-tailed bumblebee, Bombus terrestris (Apidae), is a serious invasive alien bee that is listed among Japan’s Worst 100 Invasive Alien Species (The Ecological Society of Japan, 2002). In June 2013, B. terrestris was observed visiting flowers of Alpinia zerumbet (Zingiberaceae) within the Nishihara campus of University of the Ryukyus, Okinawa-jima Island, Japan. Although escaped individuals of B. terrestris have been reported from almost all over Japan, this is the first record of this species in Okinawa Prefecture., 論文

Shun Kobayashi, Ryota Usui, Kouta Nomoto, Mineyuki Ushirokita, Tetsuo Denda, and Masako Izawa (2016) Although the stick insect Megacrania tsudai cannot fly, its eggs are dispersed by seawater, which allows the species to distribute itself widely via the ocean. The life history of this non-volant insect that establishes settlements by egg dispersal remains poorly understood. We aimed to clarify the population dynamics and effects of temperature on the eggs of M. tsudai through field observation in near the northern limits of the distribution and laboratory experiments. In the wild, all instars appeared over a period of several months, with a larger proportion of first instars emerging from December to March, and a greater number of adults being observed from June to August. Laboratory experiments showed that the hatching rate of M. tsudai was not different between conditions of 25 and 30°C, whereas it was significantly lower at 20°C. The egg-development period was shorter when eggs were maintained under high temperature conditions, and longer for eggs kept at 20°C. The effective cumulative temperature was estimated as 1561.5-2000.0°C, and the developmental zero was estimated as 12.2-13.9°C. The peak appearance of the first instar in the laboratory, which was used to obtain an estimate for the effective cumulative temperature and peak appearance of adults in the wild, was not entirely accurate because the peak appearance of the first instars in the wild was not consistently observed when the estimation indicated that they should appear. Megacrania tsudai is a univoltine near the northern limit of its distribution, and temperature has a strong effect on its egg development. Our estimation of population dynamics by laboratory experiments did not exactly predict what was observed in the field and it may be controlled by other factors. However, our findings indicate that the limiting factor of the distribution of this species is likely the effect of temperature on egg hatching.

2007年度～2009年度科学研究費補助金（基盤研究(Ｃ)）研究成果報告書, 研究概要（和文）：琉球列島に分布するニガナ属（キク科）、スイカズラ属（スイカズラ科）、アジサイ属（ユキノシタ科）などを対象に、雑種の形成や倍数化を伴う種分化の過程を形態、染色体、分子情報などを用いて解析した。本研究の結果、雑種が分布を拡大して親種を駆逐しているケースなどが確認され、閉鎖的な島嶼環境下における多様性の形成に、雑種形成や倍数化が重要な役割を果たしていることを明らかにした。, 研究概要（英文） : Hybrid and polyploid speciation within the Ryukyu Archipelago were analyzed based on morphological, cytological and molecular data. Studies on plant taxa such as the genus Ixeris (Compositae), Lonicera (Caprifoliaceae) and Hydrangea (Saxifragaceae) suggested an importance of such a speciation process to increase plant diversity within the closed insular environment.