Climate Change Cluster, Faculty of Science, University of Technology Sydney, NSW, Australia.
Institute for Evolutionary Biology, University of Edinburgh, EH8 9YL, UK.
Proc Biol Sci. 2022 Apr 27;289(1973):20212581. doi: 10.1098/rspb.2021.2581.
Evolutionary theory predicts that organismal plasticity should evolve in environments that fluctuate regularly. However, in environments that fluctuate less predictably, plasticity may be constrained because environmental cues become less reliable for expressing the optimum phenotype. Here, we examine how the predictability of +5°C temperature fluctuations impacts the phenotype of the marine diatom . Thermal regimes were informed by temperatures experienced by microbes in an ocean simulation and featured regular or irregular temporal sequences of fluctuations that induced mild physiological stress. Physiological traits (growth, cell size, complexity and pigmentation) were quantified at the individual cell level using flow cytometry. Changes in cellular complexity emerged as the first impact of predictability after only 8-11 days, followed by deleterious impacts on growth on days 13-16. Specifically, cells with a history of irregular fluctuation exposure exhibited a 50% reduction in growth compared with the stable reference environment, while growth was 3-18 times higher when fluctuations were regular. We observed no evidence of heat hardening (increasingly positive growth) with recurrent fluctuations. This study demonstrates that unpredictable temperature fluctuations impact this cosmopolitan diatom under ecologically relevant time frames, suggesting shifts in environmental stochasticity under a changing climate could have widespread consequences among ocean primary producers.
进化理论预测，生物体的可塑性应该在环境中进化，这些环境会有规律地波动。然而，在环境波动更不可预测的情况下，可塑性可能会受到限制，因为环境线索对于表达最佳表型的作用变得不太可靠。在这里，我们研究了+5°C 温度波动的可预测性如何影响海洋硅藻的表型。热区由海洋模拟中微生物经历的温度来告知，并具有诱导轻度生理压力的规则或不规则时间波动序列。使用流式细胞术在个体细胞水平上量化了生理特征（生长、细胞大小、复杂性和色素沉着）。在仅仅 8-11 天后，细胞复杂性的变化就成为了可预测性的第一个影响，随后在第 13-16 天对生长产生了有害影响。具体来说，与稳定的参考环境相比，经历不规则波动暴露的细胞的生长减少了 50%，而当波动规则时，生长增加了 3-18 倍。我们没有观察到随着反复波动而出现耐热性增强（生长越来越积极）的证据。这项研究表明，不可预测的温度波动会在生态相关的时间范围内影响这种世界性的硅藻，这表明在气候变化下环境随机性的变化可能会对海洋初级生产者产生广泛的影响。
