Oceanic island evolution in genus Sedum with specialized oceanic current dispersal ability

2021 Fiscal Year Final Research Report

• Project/Area Number: 19K16212
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 45030:Biodiversity and systematics-related
• Research Institution: Tohoku University (2020-2021); Kyoto University (2019)
• Principal Investigator: Ito Takuro 東北大学, 学術資源研究公開センター, 助教 (10827132)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: 海洋島 / 海流散布 / クローナル / 分散 / 島嶼生物学 / ベンケイソウ科 / Sedum / Crassulaceae

Outline of Final Research Achievements

It is well known that plant species on oceanic islands undergo an habitat shift from coastal to montane habitats, associated with a loss of the ability of long-distance dispersal (LDD) of "seeds and fruits". Since the montane species Sedum boninense, endemic to the Bonin Islands, is sister to the coastal species S. uniflorum from the Ryukyu Archipelago and there is a coastal population on the Muko-jima Islands, I examined the evolutionary process of this species group as a model for the oceanic island evolution.
The results showed that the Muko-jima Island pop. was a new species "Sedum mukojimense". In the past, S. uniflorum reached the Bonin Islands through the dispersal of "bulbs" by ocean currents, and S. mukojimense is thought to have speciated after secondary contact between S. boninense and S. uniflorum. Sedum boninense lost its LDD ability in the process of shifting to a montane habitat, and therefore underwent oceanic island evolution with both generality and uniqueness.

Free Research Field

進化生物学

Academic Significance and Societal Importance of the Research Achievements

聟島列島初の固有植物となるムコジママンネングサの発見は，聟島列島もまた他の島々とは異なる独自の生物相を発達させていたこと示す重要な発見となった．また，海浜植物では，種子や果実を海流にのせて長距離散布するものが多く知られているが，コゴメマンネングサの殖芽による海流散布は前例がなく，常識を覆す発見である．これは基本的に長距離散布を行わないベンケイソウ科マンネングサ属がなぜ小笠原諸島に分布しているのかという謎を解く鍵になりうる．さらにその長距離散布能力がムニンタイトゴメおよびムコジママンネングサでは鱗茎をつける進化に伴って喪失しており，一般性と特殊性を有した海洋島進化の一例を新たに示すことができた．