Natural communities are exposed to multiple environmental stressors, which simultaneously impact the population and trait dynamics of the species embedded within these communities. Given that certain traits, such as body size, are known to rapidly respond to environmental change, and given that they can strongly influence the density of populations, this raises the question of whether the strength of the eco‐phenotypic feedback loop depends on the environment, and whether stressful environments would enhance or disrupt this feedback or causal linkage. We use two competing freshwater ciliates—Colpidium striatum and Paramecium aurelia—and expose their populations to a full‐factorial design of increasing salinity and temperature conditions as well as interspecific competition. We found that salinity, temperature, and competition significantly affected the density and cell size dynamics of both species. Cell size dynamics strongly influenced density dynamics; however, the strength of this eco‐phenotypic feedback loop weakened in stressful conditions and with interspecific competition. Our study highlights the importance of studying eco‐phenotypic dynamics in different environments comprising stressful abiotic conditions and species interactions.

中文翻译：

---

生态表型反馈回路在多压力源环境中不同


自然群落受到多种环境压力源的影响，这些压力源同时影响嵌入这些群落中的物种的种群和性状动态。鉴于已知某些特征（例如体型）会迅速响应环境变化，并且它们可以强烈影响种群密度，这就提出了一个问题，即生态表型反馈回路的强度是否取决于环境，以及压力环境是否会增强或破坏这种反馈或因果联系。我们使用两种竞争性的淡水纤毛虫 — Colpidium striatum 和 Paramecium aurelia — 并将它们的种群暴露在盐度和温度条件增加以及种间竞争的全因子设计中。我们发现盐度、温度和竞争显着影响了这两个物种的密度和细胞大小动态。像胞大小动力学强烈影响密度动力学;然而，这种生态表型反馈回路的强度在压力条件和种间竞争中减弱。我们的研究强调了研究不同环境中生态表型动力学的重要性，包括压力非生物条件和物种相互作用。