Data from: When can refuges mediate the genetic effects of fire regimes? A simulation study of the effects of topography and weather on neutral and adaptive genetic diversity in fire-prone landscapes

Understanding how landscape heterogeneity mediates the effects of fire on biodiversity is increasingly important under global changes in fire regimes. We used a simulation experiment to investigate how fire regimes interact with topography and weather to shape neutral and selection-driven genetic diversity under alternative dispersal scenarios, and to explore the conditions under which micro-refuges can maintain genetic diversity of populations exposed to recurrent fire. Spatial heterogeneity in simulated fire frequency occurred in topographically-complex landscapes, with fire refuges and fire-prone ‘hotspots’ apparent. Inter-annual weather variability reduced the effect of topography on fire patterns, with refuges less apparent under high weather variability. Neutral genetic diversity was correlated with long-term fire frequency under spatially heterogeneous fire regimes, being higher in fire refuges than fire-prone areas, except under high dispersal or low fire severity (low mortality). This generated different spatial genetic structures in fire-prone and fire-refuge components of the landscape, despite similar dispersal. In contrast, genetic diversity was only associated with time since the most recent fire in flat landscapes without predictable refuges and hotspots. Genetic effects of selection driven by fire-related conditions depended on selection pressure, migration distance and spatial heterogeneity in fire regimes. Allele frequencies at a locus conferring higher fitness under successional environmental conditions followed a pattern of ‘temporal adaptation’ to contemporary conditions under strong selection pressure and high migration. However, selected allele frequencies were correlated with spatial variation in long-term mean fire frequency (relating to environmental predictability) under weak dispersal, low selection pressure and strong spatial heterogeneity in fire regimes.

在火灾制度（fire regimes）发生全球变化的背景下，解析景观异质性（landscape heterogeneity）如何调控火灾对生物多样性的影响，其重要性日益凸显。本研究借助模拟实验，探究火灾制度与地形、气象条件的交互作用如何在不同扩散情景（dispersal scenarios）下塑造中性遗传多样性（neutral genetic diversity）与选择驱动的遗传多样性（selection-driven genetic diversity），并探索微避难所（micro-refuges）维持周期性火灾胁迫下种群遗传多样性的条件。模拟火灾频率的空间异质性存在于地形复杂的景观中，且可见火灾避难所（fire refuges）与易着火"热点区域"（fire-prone ‘hotspots’）。年际气象变异性（inter-annual weather variability）会削弱地形对火灾格局的调控作用，在高气象变异性条件下，避难所的特征将不再显著。在空间异质的火灾制度下，中性遗传多样性与长期火灾频率呈正相关，火灾避难所内的中性遗传多样性高于易着火区域，但该规律在高扩散水平或低火灾烈度（低死亡率）条件下不再成立。尽管扩散模式相似，但这一现象使得景观中易着火区域与火灾避难所区域呈现出截然不同的空间遗传结构（spatial genetic structure）。与之相反，在缺乏可预测避难所与热点区域的平坦景观中，遗传多样性仅与距最近一次火灾的时间相关。火灾相关条件驱动的选择遗传效应，取决于选择压力（selection pressure）、迁移距离（migration distance）与火灾制度的空间异质性。在强选择压力与高迁移水平下，在演替环境条件下具有更高适合度（fitness）的位点等位基因频率（allele frequencies），呈现出对当代环境的"时间适应性"（temporal adaptation）模式。而在低扩散水平、低选择压力且火灾制度空间异质性较强的条件下，所选位点的等位基因频率则与长期平均火灾频率的空间变异（与环境可预测性（environmental predictability）相关）呈显著相关。