Organismal distributions are largely mediated by temperature, suggesting thermal trait variability plays a key role in defining species’ niches. We employed a trait-based approach to better understand how interand intraspecific thermal trait variability could explain diatom community dynamics using 24 strains from 5 species in the diatom genus Skeletonema, isolated from Narragansett Bay (NBay), where this genus can comprise up to 99% of the microplankton. Strain-specific thermal reaction norms were generated using growth rates obtained at temperatures ranging from −2 C to 36 C. Comparison of thermal reaction norms revealed interand intraspecific similarities in the thermal optima, but significant differences approaching the thermal limits. Cellular elemental composition was determined for two thermally differentiated species and again, the most variation occurred approaching the thermal limits. To determine the potential impact of interspecific variability on community composition, a species succession model was formulated utilizing each species’ empirically determined thermal reaction norm and historical temperature data from NBay. Seasonal succession in the modeled community resembled the timing of species occurrence in the field, but not species’ relative abundance. The model correctly predicted the timing of the dominant winter–spring species, Skeletonema marinoi, within 0–14 d of its observed peak occurrence in the field. Interspecific variability approaching the thermal limits provides an alternative mechanism for temporal diatom succession, leads to altered cellular elemental composition, and thus has the potential to influence carbon flux and nutrient cycling, suggesting that growth approaching the thermal limits be incorporated into both empirical and modeling efforts in the future. Temperature is a principal driver of global organismal distributions in both terrestrial (Angilletta 2009; Sunday et al. 2012) and marine (Poloczanska et al. 2013; García Molinos et al. 2015) environments and one of the most important environmental factors shaping microbial composition in the euphotic ocean (Sunagawa et al. 2015). Temperature differentially influences growth and cellular metabolism between organisms (Eppley 1972), which results in thermal niche differentiation among species (Hardin 1960). In microbes, the influence of temperature on growth has been used to characterize the thermal niche of a species, define thermal traits, and predict a species’ ability to respond to environmental variability (Litchman et al. 2012). For example, thermal traits have been utilized to interpret species’ thermal ranges on a global scale (Thomas et al. 2012; Boyd et al. 2013). However, the utility of thermal traits remains relatively uncharacterized in terms of their contribution to community dynamics, such as succession and seasonality. Thermal reaction norms, or performance curves, describe individual or species’ responses to a wide range of temperatures and are parameterized by the thermal traits. They peak at the thermal optima and extend to the thermal limits. Between species or individuals, thermal reaction norms can vary along the temperature axis, both in their position horizontally and in their magnitude vertically (Kingsolver 2009); two theoretical examples are depicted in Fig. 1 (adapted from Bolnick et al. 2003). In one example, species display unique growth optima along a thermal gradient that results in clear niche differentiation between species (Fig. 1a). In another example, species display similar thermal optima and niche widths resulting in less niche differentiation (Fig. 1b). While thermal reaction norms can be differentiated in a multitude of ways, greater differentiation, like that depicted in our first example, is readily observed on the global scale as species tend to assort by optima across latitudes (Thomas et al. 2012). However, on regional scales, there are insufficient data to characterize how species structure *Correspondence: rynearson@uri.edu This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes. Additional Supporting Information may be found in the online version of this article.

中文翻译：

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接近热极限的变化可以驱动硅藻群落动态

生物体分布主要由温度介导，这表明热性状变异在定义物种的生态位方面起着关键作用。我们采用了一种基于性状的方法来更好地了解种间和种内热性状变异如何解释硅藻群落动态，使用硅藻属 Skeletonema 中的 5 个物种的 24 株，从纳拉甘西特湾 (NBay) 分离，该属可占 99%的微型浮游生物。使用在 -2 C 到 36 C 的温度范围内获得的生长速率生成菌株特定的热反应规范。热反应规范的比较揭示了热优化中的种间和种内相似性，但接近热极限的显着差异。确定了两种热分化物种的细胞元素组成，然后再次确定，大多数变化发生在接近热极限。为了确定种间变异对群落组成的潜在影响，利用每个物种的经验确定的热反应规范和来自 Nbay 的历史温度数据制定了物种演替模型。模拟群落中的季节性演替类似于野外物种出现的时间，但与物种的相对丰度不同。该模型正确地预测了主要的冬春季物种 Skeletonema marinoi 的时间，该物种在野外观察到的峰值出现时间在 0-14 天之内。接近热极限的种间变异为硅藻的时间演替提供了另一种机制，导致细胞元素组成发生改变，因此有可能影响碳通量和养分循环，建议将接近热极限的增长纳入未来的实证和建模工作。温度是陆地 (Angilletta 2009; Sunday et al. 2012) 和海洋 (Poloczanska et al. 2013; García Molinos et al. 2015) 环境中全球生物分布的主要驱动因素，也是影响微生物组成的最重要环境​​因素之一在透光海洋中（Sunagawa 等人，2015 年）。温度不同地影响生物体之间的生长和细胞代谢（Eppley 1972），这导致物种之间的热生态位分化（Hardin 1960）。在微生物中，温度对生长的影响已被用来表征一个物种的热生态位，定义热特性，并预测物种对环境变化做出反应的能力（Litchman 等人，2012 年）。例如，热特性已被用于解释全球范围内物种的热范围（Thomas 等人，2012 年；Boyd 等人，2013 年）。然而，热性状的效用在它们对群落动态的贡献方面仍然相对没有特征，例如演替和季节性。热反应规范或性能曲线描述了个体或物种对各种温度的反应，并由热特性参数化。它们在热最佳值处达到峰值并扩展到热极限。在物种或个体之间，热反应规范可以沿着温度轴变化，无论是在水平位置还是在垂直大小（Kingsolver 2009）；两个理论例子如图 1 所示。1（改编自 Bolnick 等人，2003 年）。在一个例子中，物种沿着热梯度显示出独特的生长最佳状态，导致物种之间存在明显的生态位差异（图 1a）。在另一个例子中，物种表现出相似的热优化和生态位宽度，导致生态位差异较小（图 1b）。虽然可以通过多种方式区分热反应规范，但在全球范围内很容易观察到更大的差异，就像我们的第一个例子中描述的那样，因为物种往往会按最佳跨纬度进行分类（Thomas 等人，2012 年）。然而，在区域尺度上，没有足够的数据来描述物种的结构 * 通讯：rynearson@uri.edu 这是一篇基于知识共享署名-非商业性许可条款的开放获取文章，允许使用，在任何媒体中分发和复制，前提是原始作品被正确引用并且不用于商业目的。可以在本文的在线版本中找到其他支持信息。