Origins and evolution of dwarf males in marine bivalves

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K15860
• 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: Kyoto University
• Principal Investigator: Goto Ryutaro 京都大学, フィールド科学教育研究センター, 助教 (50725265)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: 性的二形 / 矮雄 / 進化 / 共生 / 繁殖集団サイズ / 分子系統解析 / 二枚貝

Outline of Final Research Achievements

Dwarf males, which are very small males that live attached to females (or hermaphrodites), are found in various taxonomic groups in the marine realm, but the conditions favoring the evolution of dwarf males remain poorly understood. In this study, I investigated the relationship between mating group size and the evolution of dwarf males, focusing on Galeommatidae, a family of tiny, diverse marine bivalves. Field and specimen surveys were conducted to obtain data on mating group size, and a comprehensive molecular phylogenetic tree was constructed. The results suggest that dwarf males have evolved independently at least seven times in this family, and lineages with dwarf males tend to have smaller mating group sizes. The findings of this study significantly contribute to a comprehensive understanding of the evolution of dwarf males, compared with other model systems.

Free Research Field

進化生態学

Academic Significance and Societal Importance of the Research Achievements

海洋では異性（雌や雌雄同体）に付着して暮らす小さな雄（矮雄）が様々な分類群で見られる。しかし、その進化条件の理解は依然として遅れてきた。本研究では、海産の小型二枚貝類であるウロコガイ科を主な対象として研究を行い、本科で7回以上独立に矮雄が起源し、繁殖集団サイズの縮小が矮雄進化を促すことを示唆した。性的二形性の進化は、進化生態学の大きな課題だが、本研究の知見はその理解に大きく寄与するものである。