Data from: Life cycle size dynamics in Didymosphenia geminata (Bacillariophytceae)

Didymosphenia geminata has received a great deal of attention in the last 25 years, and considerable effort has gone into determining the origin, ecologic impact, and economic consequences of its invasive behavior. While environmental conditions are a controlling influence in distribution, the extreme success of the species may be tied to its basic biology and life history. Little is known, however, about population dynamics, size restoration and reproduction of D. geminata. The objective of this study was to determine the temporal patterns in cell size frequency, size restoration strategy, and synchronization of life cycles between populations in close proximity. We implemented FlowCam technology to measure the length of more than 100,000 D. geminata cells from two sites in South Boulder Creek, Colorado over one year. We applied finite mixture modeling to uncover temporal patterns in size distribution. Our results show that collections of D. geminata exhibited a complex, multimodal size distribution, almost always containing four overlapping age cohorts. We failed to observe direct visual evidence of the sexual phase. Multiple abrupt and directional shifts in size distribution, however, were documented providing conclusive evidence of cell size restoration. Lastly, nodules in close proximity were asynchronous with respect to size frequency profiles and size diminution, highlighting the relevance of spatial heterogeneity in in situ diatom size dynamics. This study is the first to document the complexity of diatom cell size distribution in a lotic system, size restoration in D. geminata, and the variability in rates of size reduction at microhabitat spatial scales.

近25年来，宝石异极藻（Didymosphenia geminata）受到学界广泛关注，大量精力已投入到其入侵行为的起源、生态影响与经济后果的探究中。尽管环境条件对其分布具有调控作用，但该物种的极强入侵成功性可能与其基础生物学特性和生活史密切相关。然而，目前学界对宝石异极藻的种群动态、体型恢复与繁殖机制仍知之甚少。本研究的目标是探明种群的细胞体型频率时间分布模式、体型恢复策略，以及邻近种群间生活周期的同步性。我们借助流式成像颗粒分析系统（FlowCam），在为期一年的周期内，对美国科罗拉多州南博尔德溪两处采样点的逾10万个宝石异极藻细胞进行了长度测量。我们采用有限混合模型（finite mixture modeling）来揭示体型分布的时间模式。研究结果显示，宝石异极藻种群呈现出复杂的多峰体型分布特征，几乎始终包含四个重叠的年龄组群。我们未观测到有性生殖阶段的直接视觉证据。不过，研究记录到体型分布出现多次突发性定向偏移，这为细胞体型恢复提供了确凿证据。最后，邻近的种群在体型频率分布与体型缩减速率方面存在异步性，这凸显了空间异质性在原位硅藻体型动态中的重要意义。本研究首次在流水生境（lotic system）中揭示了硅藻细胞体型分布的复杂性、宝石异极藻的体型恢复机制，以及微生境空间尺度下体型缩减速率的变异性。