As the climate is changing, species respond by changing their distributions and abundances. The effects of climate are not only direct, but also occur via changes in biotic interactions, such as competition. Yet, the role of competition in mediating the effects of climate is still largely unclear. To examine how climate influences species performance, directly and via competition with other species, we transplanted two moss species differing in climate niches, alone and together at 59 sites along a climate gradient. Growth was monitored over three growing seasons. In the absence of competition, both species performed better under warmer conditions. Yet, when transplanted together, a warmer climate had negative effects on the northern moss, while the effects remained positive for the southern species. The negative effect of a cold climate on the southern species was larger when both species were transplanted together. Over three growing seasons, the southern species almost outcompeted the northern in warmer climates. Our results illustrate how competitive interactions can modify, and even reverse, the direct effects of climate on organism performance. A broader implication of our results is that species interactions can have important effects on how environmental and climate change influence performance and abundance.

中文翻译：

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竞争互动会改变气候的直接影响


随着气候的变化，物种通过改变它们的分布和丰度来做出反应。气候的影响不仅是直接的，而且还通过生物相互作用的变化（例如竞争）发生。然而，竞争在调节气候影响方面的作用在很大程度上仍不清楚。为了研究气候如何直接和通过与其他物种的竞争影响物种的表现，我们沿着气候梯度在 59 个地点单独或一起移植了两种气候生态位不同的苔藓物种。在三个生长季节监测生长情况。在没有竞争的情况下，这两个物种在温暖的条件下表现更好。然而，当移植在一起时，温暖的气候对北方苔藓产生了负面影响，而对南方物种的影响仍然是积极的。当两个物种一起移植时，寒冷气候对南方物种的负面影响更大。在三个生长季节中，南方物种在温暖的气候中几乎超过了北方物种。我们的研究结果表明，竞争性相互作用如何改变甚至逆转气候对生物体性能的直接影响。我们结果的更广泛含义是，物种相互作用可以对环境和气候变化如何影响性能和丰度产生重要影响。