Global average temperature, frequency of temperature extremes and amplitude of daily fluctuations are all expected to change under prospected scenarios of climate change. The amplitudes of temperature variation and the ability of species to tolerate thermal stress are crucial for species fitness and survival in rapidly changing environments. Small differences in the life histories of species or in their responses to environmental variation can differentiate their niche and support coexistence; hence, even small changes in environmental conditions may not only affect the fitness of individual species, but also the outcome of species interactions. In the present experiments, the free-living nematode species Halomonhystera disjuncta is used as a model organism to investigate physiological and behavioural responses to environmental change in an ecological context of species interactions. We examine population fitness and food-taxis behaviour of H. disjuncta under different temperature regimes in the presence and absence of a competing species. Both stressors – temperature and competition – affected life-history traits and population development of the model species in different ways; the nematode populations exhibited higher fitness under a daily fluctuating temperature regime, but a lower fitness under an increased constant temperature. The presence of a competing species had a negative effect on its population fitness and food-finding behaviour at all temperature regimes, yet the most pronounced effects of competition were observed at the highest temperatures, suggesting that interspecific interactions such as competition may weaken a species’ intrinsic tolerance to environmental change. Thermal stress thus not only affects species fitness but also species interactions, which in turn will likely have repercussions for species coexistence.

在预期的气候变化情景下，全球平均温度，极端温度的频率和每日波动的幅度都将发生变化。温度变化的幅度和物种耐受热应力的能力对于物种适应性和在快速变化的环境中生存至关重要。物种的生活史或它们对环境变化的反应中的微小差异可以区分它们的生态位并支持共存；因此，即使环境条件发生很小的变化，也不仅会影响单个物种的适应性，还会影响物种相互作用的结果。在本实验中，自由生存的线虫物种Halomonhystera disjuncta用作模型生物，以研究物种相互作用的生态环境中对环境变化的生理和行为响应。我们研究了H. disjuncta的种群适应度和食物出租车行为在存在和不存在竞争物种的情况下，在不同的温度范围内。温度和竞争这两个压力源都以不同方式影响了模型物种的生活史特征和种群发展；线虫种群在每天波动的温度下显示出较高的适应性，而在恒定温度下显示出较低的适应性。在所有温度条件下，竞争物种的存在都会对其种群适应度和食物寻找行为产生负面影响，但是在最高温度下观察到竞争最明显的影响，这表明种间相互作用（例如竞争）可能会削弱物种的生存能力。对环境变化的内在宽容。因此，热应力不仅影响物种适应性，还影响物种相互作用，