Data from: Haemoglobin-mediated response to hyper-thermal stress in the keystone species Daphnia magna

Anthropogenic global warming has become a major geological and environmental force driving drastic changes in natural ecosystems. Due to the high thermal conductivity of water and the effects of temperature on metabolic processes, freshwater ecosystems are among the most impacted by these changes. The ability to tolerate changes in temperature may determine species long-term survival and fitness. Therefore, it is critical to identify coping mechanisms to thermal and hyper-thermal stress in aquatic organisms. A central regulatory element compensating for changes in oxygen supply and ambient temperature is the respiratory protein haemoglobin (Hb). Here, we quantify haemoglobin (Hb) plastic and evolutionary response in D. magna (sub)populations resurrected from the sedimentary archive of a lake with known history of increase in average temperature and recurrence of heat waves. By measuring constitutive changes in crude Hb protein content among (sub)populations we assessed evolution of the haemoglobin gene family in response to temperature increase. To quantify the contribution of plasticity in the response of this gene family to hyper-thermal stress, we quantified changes in Hb content in all (sub)populations under hyper-thermal stress as compared to non-stressful temperature. Further, we tested competitive abilities of genotypes as a function of their Hb content, constitutive and induced. We found that haemoglobin (Hb)-rich genotypes have superior competitive abilities as compared to Hb-poor genotypes under hyper-thermal stress after a period of acclimation. These findings suggest that whereas long-term adjustment to higher occurrence of heat waves may require a combination of plasticity and genetic adaptation, plasticity is most likely the coping mechanism to hyper-thermal stress in the short term. Our study suggests that with higher occurrence of heat waves Hb-rich genotypes may be favoured with potential long-term impact on population genetic diversity

人为全球变暖已成为驱动自然生态系统发生剧烈变化的关键地质与环境营力。由于水体热导率较高，且温度会对代谢过程产生影响，淡水生态系统是受此类变化影响最显著的生态系统之一。物种耐受温度波动的能力，或决定其长期存活与适合度。因此，探明水生生物应对热胁迫与极端高温胁迫的适应机制，具有重要研究价值。呼吸蛋白血红蛋白（haemoglobin, Hb）是补偿氧气供应与环境温度变化的核心调控因子。本研究对从某已知年均温上升、热浪频发的湖泊沉积物档案中复活的大型溞（D. magna）亚种群的血红蛋白可塑性响应与进化响应进行了定量分析。通过测定各亚种群中粗制Hb蛋白含量的组成型变化，我们评估了血红蛋白基因家族在温度升高胁迫下的进化模式。为量化该基因家族的可塑性响应在应对极端高温胁迫时的贡献，我们分别测定了所有亚种群在极端高温胁迫与非胁迫温度条件下的Hb含量变化并进行对比。此外，我们还根据基因型的组成型与诱导型Hb含量，检测了其竞争能力。研究发现，在经过一段时期的适应性驯化后，极端高温胁迫下富含Hb的基因型的竞争能力显著优于Hb含量较低的基因型。本研究结果表明，若要长期适应热浪频发的环境，可能需要结合表型可塑性与遗传适应两种策略；但从短期来看，表型可塑性极有可能是应对极端高温胁迫的主要适应机制。本研究表明，随着热浪发生频率的升高，富含Hb的基因型将更具生存优势，这可能会对种群的遗传多样性产生潜在的长期影响。