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.

确定动物在种群恢复（population recovery）过程中的来源，有助于理解干扰事件与干扰制度（disturbance regimes）对物种分布及遗传多样性（genetic diversity）的影响。受火灾影响的动物种群，其恢复路径主要包含三种：外部重新定植（external recolonization）、源自庇护所的成核恢复（nucleated recovery），以及原位（in situ）存活与种群增长。我们通过模拟实验构建了与上述三种恢复模型相对应的生态学与遗传学特征假说，并针对一场规模超5万公顷的严重野火后两种小型哺乳动物的种群恢复展开研究，对上述假说进行验证。本研究的对象为澳洲林鼠（Australian bush rat）与敏捷袋鼩（agile antechinus）两种小型哺乳动物。

野火严重降低了两个物种种群的种群丰度（abundance），但二者均在两代之内恢复至火灾前水平甚至更高；不过我们的研究结果拒绝了"通过外部重新定植实现种群恢复"的假说。尽管遗传学（genetic）证据显示，敏捷袋鼩的扩散能力（dispersal capacity）远强于澳洲林鼠，但在种群恢复阶段，两个物种的种群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（gradient）。

种群恢复由局域尺度（local-scale）过程主导，但不同物种的恢复机制存在差异，这源于火灾对栖息地适宜性（habitat suitability）的空间影响。敏捷袋鼩种群通过原位存活个体的种群增长实现恢复；而澳洲林鼠则遵循成核恢复模型，即通过地形排水线（topographic drainage lines）内的微型庇护所开展局域重新定植。

澳洲林鼠的成核恢复过程与扩散模式改变及精细尺度（fine-scale）的遗传混合（genetic admixture）特征相关。我们发现，在恢复阶段雌性个体的扩散（dispersal）能力有所提升，这与未受干扰森林中雄性偏倚扩散（male-biased dispersal）的模式形成鲜明对比。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。

本研究表明，由火灾对资源分布的影响所决定的存活个体初始分布（initial distribution of survivors），如何决定了后续种群恢复格局的尺度效应（scaling），以及种群分布与遗传多样性对干扰制度变化的响应敏感性。