Non-native species and climate change pose serious threats to global biodiversity. However, the roles of climate, dispersal, and competition are difficult to disentangle in heterogeneous landscapes. We combine empirical data and theory to examine how these forces influence the spread of non-native species in Lake Baikal. We analyze the potential for Daphnia longispina to establish in Lake Baikal, potentially threatening an endemic, cryophillic copepod Epischurella baikalensis. We collected field samples to establish current community composition and compared them to model predictions informed by flow rates, present-day temperatures, and temperature projections. Our data and model agree that expansion is currently limited by dispersal. However, projected increases in temperature reverse this effect, allowing D. longispina to establish in Lake Baikal’s main basin. A strong negative impact emerges from the interaction between climate change and dispersal, outweighing their independent effects. Climate, dispersal, and competition have complex, interactive effects on expansion with important implications for global biodiversity.

外来物种和气候变化对全球生物多样性构成严重威胁。然而，气候、扩散和竞争的作用很难在异质景观中解开。我们结合经验数据和理论来研究这些力量如何影响贝加尔湖非本地物种的传播。我们分析了水蚤在贝加尔湖建立的潜力，可能威胁到一种地方性的、嗜冷的桡足类Epischurella baikalensis. 我们收集了现场样本以建立当前的群落组成，并将它们与根据流速、当前温度和温度预测得出的模型预测进行比较。我们的数据和模型同意，扩张目前受到分散的限制。然而，预计的温度升高会逆转这种影响，允许D。longispina建立在贝加尔湖的主要盆地。气候变化和扩散之间的相互作用产生了强烈的负面影响，超过了它们的独立影响。气候、扩散和竞争对扩张具有复杂的交互影响，对全球生物多样性具有重要影响。