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 microrefuges 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. Interannual 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.

在火动态（fire regimes）发生全球变化的当下，厘清景观异质性（landscape heterogeneity）对火效应的调控机制，对于理解火对生物多样性（biodiversity）的影响愈发关键。本研究借助模拟实验（simulation experiment），探究了不同扩散情景（dispersal scenarios）下，火动态与地形（topography）、气象（weather）因子的互作如何塑造中性遗传多样性（neutral genetic diversity）与选择驱动型遗传多样性（selection-driven genetic diversity），并解析了微避难所（microrefuges）能够维持反复受火干扰种群遗传多样性的条件。在地形复杂的景观中，模拟火频率（fire frequency）呈现空间异质性（spatial heterogeneity），火避难所（fire refuges）与易火热点（fire-prone hotspots）清晰可见。年际气象变率（interannual weather variability）会削弱地形对火分布格局（fire patterns）的调控作用，在气象变率较高的情境下，火避难所的辨识度会降低。在空间异质的火动态下，中性遗传多样性与长期火频率呈显著相关：火避难所内的中性遗传多样性高于易火区域，但在高扩散或低火烈度（fire severity，低死亡率（mortality））的情境下除外。尽管扩散模式一致，这一差异仍使得易火区域与火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，在无明确避难所与热点区域的平坦景观（flat landscapes）中，遗传多样性仅与末次火事件发生后的间隔时长相关。火相关环境驱动的选择对遗传多样性的影响，取决于选择压力（selection pressure）、迁移距离（migration distance）以及火动态的空间异质性。在强选择压力与高迁移水平下，在演替环境条件（successional environmental conditions）中赋予更高适合度（fitness）的基因座（locus）的等位基因频率（allele frequencies），呈现出对当前环境的“时间适应性（temporal adaptation）”模式。但在低扩散（weak dispersal）、低选择压力且火动态空间异质性较强的情境下，受选择位点的等位基因频率与长期平均火频率的空间变异（与环境可预测性（environmental predictability）相关）呈显著相关。