Ecological mechanisms and genetic base for the coexistence of multiple clonal populations: an analytical study with obligate parthenogenetic Daphnia species

2018 Fiscal Year Final Research Report

• Project/Area Number: 16H02522
• Research Category: Grant-in-Aid for Scientific Research (A)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Ecology/Environment
• Research Institution: Tohoku University
• Principal Investigator: Jotaro Urabe 東北大学, 生命科学研究科, 教授 (50250163)
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: ミジンコ / 遺伝的多様性 / 多種共存機構 / 消費型競争 / 休眠卵 / ニッチ分化 / 遺伝率 / 侵入種

Outline of Final Research Achievements

Competitive inferior species can be frequently found with competitively superior species. However, it is not necessarily clear why such a coexistence is possible. In this study, ecological mechanisms enabling the coexistence of competitive species were examined using genotypes in obligate parthenogenetic Daphnia pulex that were invaded from north America. Genetic analyses, common garden experiments and field observations showed that a number of heritable traits have been evolved in this species after the invasion into Japan. Among these, frequency of the resting egg production was one of the heritable traits that could be easily changed and was high in competitively inferior genotypes. In addition, it was revealed that competitively inferior genotypes could avoid competition with competitively superior genotypes by producing frequently the resting eggs. These results support an importance of storage hypothesis as a mechanism for the sympatric coexistence of competitive species.

Free Research Field

生態学

Academic Significance and Societal Importance of the Research Achievements

限られた資源や生息空間では、競争が激化するため、競争に優位な種だけが生残するようになり、結果として種多様性は減少する。しかし、野外個体群では、潜在的に競争関係にある種の共存は稀ではない。本研究では、多様な個体群が共存できる仕組みとして様々な説の中から、競争劣位種が休眠卵生産を高めることで絶滅を逃れ、長期共存を可能にし、集団の多様性を維持していることを明らかにした。この結果は、これまで多種共存について注目されてこなかったStorage仮説を支持するものであり、休眠ステージが競争回避や生息場所の種多様性維持に重要な機能を果たしていることを示している。