Data from: Spatial variation in Allee effects influences patterns of range expansion

Allee effects are thought to slow range expansion and contribute to stable range boundaries. Recent studies have shown Allee effects to vary spatiotemporally due to influences of environmental heterogeneity on population processes. Gradients in Allee effects might occur as a species' range approaches suboptimal conditions while expanding into new territory. Allee effects could exhibit patchiness if drivers of positive density dependence (e.g., mate finding rates) are influenced by habitat patchiness. However, theoretical studies have largely assumed Allee effects to be spatially constant. The goal of this study was to evaluate how spatiotemporal patterns of range expansion respond to spatial variations in Allee effects. We simulated spread in landscapes that differed in the spatial configuration and range of Allee thresholds. We compared spread with a constant Allee effect to spread in landscapes where the Allee threshold varied along a gradient or in a patchy fashion. Landscape configuration affected patterns of range expansion when Allee thresholds were near or exceeded the number of colonizing immigrants. In gradient landscapes, spread decelerated as the range edge approached higher Allee thresholds. In patchy landscapes, spread advanced quickly through areas with lower Allee thresholds and stalled in areas with higher Allee thresholds. Both focal and neighboring locations influencing spread. Spatial variation in Allee effects may be an underappreciated source of heterogeneity in patterns of range expansion. When Allee effects vary, spread estimates based on a spatially averaged Allee threshold may not accurately predict realized rates of spread. Our findings suggest that spread can occur despite generally high Allee thresholds if Allee thresholds are low in a subset of patches. This result has negative implications for controlling the spread of invasive species, but it also suggests range shifts by native species in response to climate change may be possible with even sparsely distributed refugia from Allee effects.阿利效应（Allee effects）被认为能够延缓种群扩布进程，并促成稳定的种群分布范围边界。近期研究表明，受环境异质性对种群过程的影响，阿利效应会呈现时空动态变化。当物种向新领地扩张并逐渐接近其适生范围的亚适生条件时，阿利效应可能会呈现梯度分布格局。若正密度依赖的驱动因子（如觅偶成功率）受到生境斑块性的影响，阿利效应则可能呈现斑块化特征。然而，过往理论研究大多假定阿利效应在空间上是恒定不变的。本研究旨在探究种群扩布的时空格局如何响应阿利效应的空间变异。我们在空间配置与阿利阈值范围各不相同的景观中模拟了种群扩布过程，并将恒定阿利效应下的扩布模式，与阿利阈值沿梯度变化或呈斑块化分布的景观中的扩布模式进行了对比。当阿利阈值接近或超过定植个体的数量时，景观格局会显著影响种群扩布格局。在梯度景观中，随着种群范围边缘趋近更高的阿利阈值，扩布进程会逐渐减速。在斑块化景观中，种群会快速通过阿利阈值较低的区域，而在阿利阈值较高的区域停滞不前。焦点斑块与邻近区域均会对种群扩布过程产生影响。阿利效应的空间变异或许是种群扩布格局中一种尚未被充分重视的异质性来源。当阿利效应存在空间变异时，基于空间平均阿利阈值的扩布预测可能无法准确反映实际的扩布速率。我们的研究结果表明，即便整体阿利阈值较高，若部分斑块内的阿利阈值较低，种群仍可实现扩布。这一结论对于入侵物种的扩散防控具有负面启示，但同时也表明，本土物种为响应气候变化而进行的分布范围转移，即便仅存在零星分布的阿利效应避难所，也具备实现的可能性。