Kowalski Jessica J, Gilbert Benjamin, Strauss Sharon Y, Germain Rachel M
Department of Zoology, Biodiversity Research Centre, University of British Columbia, Vancouver, BC V6T 1Z4.
Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON M5S 3B2.
Proc Natl Acad Sci U S A. 2025 Sep 16;122(37):e2422454122. doi: 10.1073/pnas.2422454122. Epub 2025 Sep 10.
The size and composition of local species pools are, in part, determined by past dispersal events. Predicting how communities respond to future disturbances, such as fluctuating environmental conditions, requires knowledge of such histories. We assessed the influence of a historical dispersal event on community assembly by simulating various scales of dispersal for 240 serpentine annual plant communities that experienced a large shift from drought to high rainfall conditions over three years. We collected, aggregated, and redistributed the aboveground seed bank (i.e., all loose seed present on the soil surface before the growing season initiates) from 30 sites across five nested spatial scales ([Formula: see text]1 m, 5 m, 100 m, 5 km, and 10 km), and annually censused communities to identify change in community structure among dispersal scales and over time. Our one-time dispersal manipulation diversified aboveground seed banks, provided insurance against temporal variability at intermediate and large dispersal distances ([Formula: see text]100 m), and even supported community reassembly toward a new compositional state at the 10 km scale. We also found evidence that temporal lags directed community responses to environmental fluctuations, preventing rare species extirpations and providing subordinate species discrete windows of time to supplement their seed banks. Our results reveal a joint spatiotemporal equilibrium in this system where dispersal through space interacts with temporal fluctuations in climate to support species' persistence via aboveground seed banks. This experiment underscores the importance of dispersal for diversity maintenance in this global biodiversity hotspot, where the magnitude and frequency of future climate fluctuations is uncertain.
当地物种库的规模和组成部分取决于过去的扩散事件。预测群落如何应对未来的干扰，如环境条件的波动，需要了解这些历史情况。我们通过模拟240个蛇纹石一年生植物群落的不同扩散尺度，评估了一次历史扩散事件对群落组装的影响，这些群落在三年间经历了从干旱到高降雨条件的巨大转变。我们从五个嵌套空间尺度（1米、5米、100米、5公里和10公里）的30个地点收集、汇总并重新分配了地上种子库（即生长季节开始前土壤表面存在的所有松散种子），并每年对群落进行普查，以确定扩散尺度之间以及随时间变化的群落结构变化。我们一次性的扩散操作使地上种子库多样化，为中等和大扩散距离（100米）的时间变异性提供了保障，甚至在10公里尺度上支持群落重新组装成新的组成状态。我们还发现有证据表明，时间滞后引导群落对环境波动做出反应，防止稀有物种灭绝，并为从属物种提供离散的时间窗口来补充它们的种子库。我们的结果揭示了这个系统中时空联合平衡，即通过空间的扩散与气候的时间波动相互作用，通过地上种子库来支持物种的持续存在。该实验强调了扩散对于这个全球生物多样性热点地区多样性维持的重要性，在该地区未来气候波动的幅度和频率尚不确定。
