Data from: Where do animals come from during post-fire population recovery? Implications for ecological and genetic patterns in post-fire landscapes

Identifying where animals come from during population recovery can help to understand the impacts of disturbance events and regimes on species distributions and genetic diversity. Alternative recovery processes for animal populations affected by fire include external recolonization, nucleated recovery from refuges, or in situ survival and population growth. We used simulations to develop hypotheses about ecological and genetic patterns corresponding to these alternative models. We tested these hypotheses in a study of the recovery of two small mammals, the Australian bush rat and the agile antechinus, after a large (>50,000 ha), severe wildfire.

The abundance of both species was severely reduced by fire and recovered to near or above pre-fire levels within two generations, yet we rejected a hypothesis of recovery by external recolonization. While the agile antechinus showed genetic evidence for far greater dispersal capacity than the bush rat, neither species showed gradients in abundance or genetic diversity with distance from unburnt forest during population recovery.

Population recovery was driven by local-scale processes. However, the mechanisms differed between species, resulting from the spatial impacts of fire on habitat suitability. Agile antechinus populations recovered through population growth from in situ survivors. The bush rat followed a model of nucleated recovery, involving local recolonization from micro-refuges in topographic drainage lines.

Nucleated recovery by the bush rat was associated with changes in dispersal, and fine-scale patterns of genetic admixture. We identified increased dispersal by females during recovery, contrasting with male-biased dispersal in unburnt forest. Such flexibility in dispersal can potentially increase recovery rates compared to expectations based on dispersal behavior within undisturbed populations.

Our study shows how the initial distribution of survivors, determined by fire effects on resource distribution, determines the subsequent scaling of population recovery patterns, and the sensitivity of population distribution and genetic diversity to changing disturbance regimes.

明确种群恢复过程中动物的来源，有助于理解干扰事件与干扰制度对物种分布及遗传多样性的影响。受火灾影响的动物种群，其恢复途径可分为三类：外部重新定殖（external recolonization）、来自庇护所的成核恢复（nucleated recovery），以及原位（in situ）存活与种群增长。本研究通过模拟推演对应上述不同恢复模型的生态学与遗传模式假说，并针对一场面积超5万公顷的严重野火后，两种小型哺乳动物——澳洲林鼠（Australian bush rat）与敏捷袋鼩（Agile antechinus）的种群恢复过程开展了假说验证。

野火导致两种小型哺乳动物的种群丰度大幅下降，但二者均在两代内恢复至接近甚至超过火灾前的种群水平；据此我们排除了外部重新定殖驱动种群恢复的假说。尽管敏捷袋鼩在遗传层面展现出远强于澳洲林鼠的扩散能力，但在种群恢复过程中，两种动物的丰度与遗传多样性均未随距未烧森林的距离呈现梯度变化。

种群恢复由局域尺度的过程主导，但不同物种的恢复机制存在差异，这源于火灾对生境适宜性的空间影响。敏捷袋鼩的种群恢复依托原位存活个体的种群增长；而澳洲林鼠则遵循成核恢复模型，即通过地形汇水线区域的微庇护所开展局域重新定殖。

澳洲林鼠的成核恢复与扩散模式变化及精细尺度的遗传混合（genetic admixture）特征相关。本研究发现，在恢复过程中雌性个体的扩散行为显著增强，这与未受干扰森林中雄性偏向的扩散模式形成鲜明对比。相较于基于未受干扰种群扩散行为的预期，这种扩散灵活性或可提升种群恢复速率。

本研究揭示了：由火灾对资源分布的影响所决定的存活个体初始分布，如何决定后续种群恢复模式的尺度效应，以及种群分布与遗传多样性对干扰制度变化的敏感性。