Department of Hydrobiology and Protection of Ecosystems, University of Life Sciences, B. Dobrzańskiego 37, 20-262 Lublin, Poland.
Sci Total Environ. 2020 Jun 25;723:137963. doi: 10.1016/j.scitotenv.2020.137963. Epub 2020 Mar 19.
The consequences of raising temperatures have been intensively studied by biologists and ecologists for the past few decades. However, current climatic changes also include many anomalous weather events, such as intra-seasonal heatwaves followed by immediate decreases in temperature. In this study, the responses of population development and life history traits to different thermal regimes were investigated. The freshwater water flea Daphnia magna (Cladocera, Crustacea) was used as a model organism. Daphnia magna populations were monitored under temperature regimes of warm (25 °C), cold (5 °C), synchronous (gradual changes between 25 °C and 5 °C) or stochastic (random changes between 25 °C and 5 °C). Population size of D. magna populations decreased with unpredictability of thermal conditions; the highest density of D. magna was found in the warm environment and the lowest density in the stochastic environment. Thermal regime had significant impact on the prevalence of asexual and sexual reproduction of D. magna. Under a synchronous regime, an accumulation of asexual reproduction was observed during cold episodes; this was followed by a phase of population disturbance, manifesting itself in high fluctuations of asexual reproduction and a pattern of sexual reproduction typical of a cold regime. Under a stochastic regime, the population disturbances were observed throughout the duration of the experiment. Daily observations of individual life history traits revealed that the development of populations under different thermal regimes resulted from the regime-specific survivability of neonates. Population development was also affected by the frequency of reproduction, which consisted of the number of broods carried per lifetime. The results indicate that not only temperature but also shifts in thermal conditions have an important influence on individual life history traits and population dynamics of D. magna. It is important to consider the effects of shifts in water temperature on demographic and individual traits simultaneously because the impact of thermal changes on population traits can be modified by individual life histories.
在过去的几十年里，生物学家和生态学家已经深入研究了升温的后果。然而，当前的气候变化还包括许多异常天气事件，例如季节内热浪随后立即降温。在这项研究中，研究了种群发展和生活史特征对不同热环境的反应。淡水水蚤（Daphnia magna）（甲壳纲，甲壳动物）被用作模式生物。在温暖（25°C）、寒冷（5°C）、同步（25°C 和 5°C 之间逐渐变化）或随机（25°C 和 5°C 之间随机变化）的温度条件下监测 Daphnia magna 种群。Daphnia magna 种群的大小随热条件的不可预测性而减少；Daphnia magna 的最高密度出现在温暖的环境中，最低密度出现在随机的环境中。热环境对 Daphnia magna 无性和有性繁殖的流行有显著影响。在同步环境下，在寒冷期观察到无性繁殖的积累；随后是种群干扰阶段，表现为无性繁殖的高波动和典型的寒冷环境的有性繁殖模式。在随机环境下，整个实验过程中都观察到种群干扰。对个体生活史特征的每日观察表明，不同热环境下的种群发展是由新生儿特定的存活率决定的。种群发展也受到繁殖频率的影响，繁殖频率包括一生中携带的产卵次数。结果表明，不仅温度，而且热条件的变化对 Daphnia magna 的个体生活史特征和种群动态都有重要影响。同时考虑水温变化对人口和个体特征的影响很重要，因为热变化对种群特征的影响可以通过个体生活史来改变。
