When and how did Japanese allotetraploid fern species of which both parent species are extant in Japan originate?

2021 Fiscal Year Final Research Report

• Project/Area Number: 19K06804
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 45030:Biodiversity and systematics-related
• Research Institution: Chiba University
• Principal Investigator: Watano Yasuyuki 千葉大学, 大学院理学研究院, 教授 (70192820)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: 異質倍数体 / シダ植物 / 生態的ニッチモデリング / ニッチシフト仮説 / 二次接触仮説 / 気候変動

Outline of Final Research Achievements

The successful establishment of polyploid species is hypothesized to be promoted by niche differentiation from the parental species. However, this ecological aspect of allopolyploid speciation remains controversial. In order to accumulate empirical data and find a trend, we tried to find new cases in that all of the parental diploid and allotetraploid species (trios) exist in the Japanese archipelago, suggesting that the allopolyploid species are likely to have originated in Japan. As a result, we found five new cases. Climate niche analyses on the trios of Lepisorus nigripes and L. yamaokae suggested that more opportunities for hybridization during the Last Glacier Maximum (ca. 2.1 mya).

Free Research Field

植物分類学

Academic Significance and Societal Importance of the Research Achievements

日本列島内で起源した可能性が高い「日本産異質４倍体シダ植物種の中で、その祖先二倍体種が共に日本列島に現存する」事例を新規に5件発見した。既知の6例と合わせ、異質倍数体種とその両親種の間の生態的ニッチ分化パターンの理解のための基盤が揃ったと言える。事例の中には両親種のニッチが大きく違い、現環境下では親種間の交雑の機会がないものもある。これらの事例では、第四紀における気候変動（氷期-間氷期）に伴う分布の変化が親種間の交雑の機会を与え、さらに倍数体種の定着を促進した可能性がある。