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.解析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，其恢复过程存在三类备选路径：外部重新定植（external recolonization）、源自避难所的成核恢复（nucleated recovery），以及原位存活（in situ survival）与种群增长。我们通过模拟实验构建了与上述三类恢复模型对应的生态与遗传格局假说，并在一场面积超5万公顷的严重野火后，针对两种小型哺乳动物——澳洲灌丛鼠（Australian bush rat）与敏捷袋鼩（agile antechinus）——的种群恢复开展了假说验证研究。两种小型哺乳动物的种群丰度均因火灾遭受严重下降，但在两代以内便恢复至接近甚至超过火灾前的水平；不过我们否定了种群恢复依赖外部重新定植的假说。尽管敏捷袋鼩的遗传证据显示其扩散能力远强于澳洲灌丛鼠，但在种群恢复过程中，两个物种的种群丰度与遗传多样性均未随与未过火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。敏捷袋鼩的种群通过原位存活个体的种群增长实现恢复；而澳洲灌丛鼠则遵循成核恢复模型，即借助地形沟谷地带的微避难所开展局域重新定植。澳洲灌丛鼠的成核恢复过程，与扩散行为改变及遗传混合的精细格局存在关联。我们发现种群恢复过程中雌性的扩散行为有所增加，这与未过火林中雄性偏向的扩散模式形成鲜明对比。相较于未受干扰种群基于扩散行为的预期，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格局的尺度效应，以及种群分布与遗传多样性对干扰制度变化的响应敏感性。