Data from: Colonization and demographic expansion of freshwater fauna across the Hawaiian Archipelago

It is widely accepted that insular terrestrial biodiversity progresses with island age because colonization and diversification proceed over time. Here we assess whether this principle extends to oceanic island streams. We examined range-wide mtDNA sequence variation in four stream-dwelling species across the Hawaiian archipelago to characterize the relationship between colonization and demographic expansion, and to determine whether either factor reflects island age. We found that colonization and demographic expansion are not related and that neither correspond to island age. The snail Neritina granosa exhibited the oldest colonization time (~2.713 mya) and time since demographic expansion (~282 kya), likely reflecting a preference for lotic habitats most prevalent on young islands. Conversely, gobioid fishes (Awaous stamineus, Eleotris sandwicensis and Sicyopterus stimpsoni) colonized the archipelago only ~0.411-0.935 mya, suggesting ecological opportunities for colonization in this group were temporally constrained. These findings indicate that stream communities form across colonization windows, underscoring the importance of ecological opportunities in shaping island freshwater diversity.

学界普遍认为，岛屿陆生生物多样性随岛屿年龄增长而提升，这是因为物种定殖与多样化过程随时间推进持续进行。本研究旨在验证这一规律是否同样适用于大洋岛屿溪流生态系统。我们针对夏威夷群岛范围内4种溪流栖息物种的全分布区线粒体DNA（mtDNA）序列变异展开分析，旨在刻画物种定殖与种群扩张之间的关联，并探究这两个过程是否与岛屿年龄存在对应关系。研究结果显示，物种定殖与种群扩张之间并无显著关联，且二者均与岛屿年龄不存在对应关系。其中蜗牛*Neritina granosa*的定殖时间（约2.713 mya，即271.3万年前）与种群扩张后时长（约282 kya，即28.2万年前）均为所有研究类群中最久，这大概率反映出该物种偏好栖息于年轻岛屿上最为常见的流水生境。与之相反，𫚥虎鱼类（*Awaous stamineus*、*Eleotris sandwicensis*及*Sicyopterus stimpsoni*）的定殖时间仅为约0.411~0.935 mya，即41.1万至93.5万年前，这表明该类群的定殖生态机会在时间维度上受到限制。上述研究结果表明，溪流群落的形成存在特定的定殖窗口期，这凸显了生态机会在塑造岛屿淡水生物多样性过程中的核心重要性。