Effects of fire regime on the population genetics of natural pine stands, in Genetic structure of forest trees in biodiversity hotspots at different spatial scales (Ph.D. thesis).

The recurrence of wildfires is predicted to increase worldwide due to climate change, resulting in severe impacts on biodiversity and ecosystem functioning. We used simple sequence repeat (SSR) and single nucleotide polymorphism (SNP) markers to examine the effects of fire regime on genetic diversity, demographic history and fine-scale spatial genetic structure (SGS) of Pinus pinaster and P. halepensis, two conifers with similar adaptations to fire in the eastern Iberian Peninsula. Stands growing under high (HiFi) or low (LoFi) frequency of crown fires had similar levels of genetic diversity and similar demographic history, with bottlenecks detected in all stands in both species. HiFi populations were not genetically depleted, suggesting that adaptations such as a diverse canopy seed bank due to serotinous cones, an early age of first flowering and high gene flow buffer against possible reductions of genetic diversity. Significantly stronger SGS at SNPs in HiFi than LoFi stands of P. halepensis suggested fire-related altered dispersal possibly combined with microenvironmental selection in this fire-sensitive “seeder” species. In contrast, SGS at SNP markers was unrelated to fire regime in P. pinaster. This could be a consequence of more pronounced fire-resistance in this species enabling some adults to survive fire, hence causing a lower dependence on post-fire regeneration. Our results highlight that the impact of fire differs in species with similar life-history traits. Therefore, species-specific studies are needed to understand the role of wildfires for the evolution of future forests

气候变化预计将导致全球野火发生频次持续攀升，对生物多样性与生态系统功能造成严重冲击。本研究采用简单序列重复（simple sequence repeat, SSR）与单核苷酸多态性（single nucleotide polymorphism, SNP）标记，探究了火制度对伊比利亚半岛东部两种火适应性相似的针叶树种——海岸松（Pinus pinaster）与阿勒颇松（Pinus halepensis）的遗传多样性、种群历史动态及精细尺度空间遗传结构（fine-scale spatial genetic structure, SGS）的影响。研究选取了冠火发生频率较高（HiFi）与较低（LoFi）的林分，结果显示两个物种的各类林分均具有相似的遗传多样性水平与种群历史动态，且所有林分均检测到种群瓶颈效应。HiFi种群未出现遗传损耗，这表明诸如宿存球果形成的多样冠层种子库、较早的首次开花年龄以及较高的基因流等适应性特征，可缓冲遗传多样性可能出现的下降。对于阿勒颇松，HiFi林分中基于SNP标记的精细尺度空间遗传结构显著强于LoFi林分，这提示与火灾相关的扩散模式改变，可能结合该火敏感型种子更新物种的微环境选择共同发挥作用。与之相反，海岸松的SNP标记空间遗传结构与火制度并无关联。这或许是因为该物种耐火性更强，部分成体可在火灾中存活，因此对火灾后更新的依赖程度更低。本研究结果凸显出：即便生活史特征相似的物种，其对火灾的响应也存在差异。因此，需开展物种特异性研究，以明晰野火在未来森林演化中的作用。