Habitat-mediated carry-over effects lead to context dependent outcomes of species interactions

1. When individuals disperse, their performance in newly colonized habitats can be influenced by the conditions they experienced in the past, leading to environmental carry-over effects. While carry-over effects are ubiquitous in animal and plant systems, their impact on species interactions and coexistence are largely ignored in traditional coexistence theory. 2. Here we used a combination of modelling and experiments with two competing species to examine when and how such environmental carry-over effects influence community dynamics and competitive exclusions. 3. We found that variation in the natal habitat quality of colonizing individuals created carry-over effects which altered competitive coefficients, fecundity and mortality rates, and extinction probabilities of both species. As a consequence, the dynamics of competitive exclusion within and across habitat types was contingent on the natal habitat of colonizing individuals, indicating that spatial carry-over effects can fundamentally alter the dynamics and outcome of interspecific competition. 4. Interestingly, carry-over effects persistently influenced dynamics in systems with interspecific competition for the entire duration of the experiment while carry-over effects were transient and only influenced initial dynamics in single-species populations. Thus carry-over effects can be enhanced by species interactions, suggesting that their long-term effects may often not be accurately predicted by single-species studies. 5. Given that carry-over effects are ubiquitous in heterogeneous landscapes, our results provide a novel mechanism that could help explain variation in the structure of natural communities.

1. 当个体发生扩散时，其在新定植生境中的生长表现会受到过往经历的环境条件影响，进而产生环境遗留效应（environmental carry-over effects）。尽管遗留效应在动植物系统中广泛存在，但传统物种共存理论在很大程度上忽视了其对物种相互作用与物种共存的影响。2. 本研究结合模型构建与两种竞争物种的控制实验，探究了此类环境遗留效应影响群落动态与竞争排除的具体时机与作用方式。3. 研究结果表明，定植个体的出生栖息地质量差异会催生遗留效应，进而改变两个物种的竞争系数、繁殖率与死亡率，以及二者的种群灭绝概率。由此可见，不同生境类型内部及跨生境的竞争排除动态，均取决于定植个体的出生栖息地，这说明空间尺度的遗留效应能够从根本上改变种间竞争的动态过程与最终结果。4. 值得注意的是，在整个实验周期内，存在种间竞争的系统中遗留效应会持续影响群落动态；而在单物种种群中，遗留效应仅为瞬时性的，仅作用于种群初始动态阶段。因此，物种间的相互作用能够强化遗留效应，这意味着单物种种群研究往往无法准确预测遗留效应的长期影响。5. 鉴于遗留效应在异质性景观中普遍存在，本研究结果提出了一种全新的机制，可为解释自然群落结构的变异提供理论支撑。