Data from: Field heritability of a plant adaptation to fire in heterogeneous landscapes

The strong association observed between fire regimes and variation in plant adaptations to fire suggests a rapid response to fire as an agent of selection. It also suggests that fire-related traits are heritable, a precondition for evolutionary change. One example is serotiny, the accumulation of seeds in unopened fruits or cones until the next fire, an important strategy for plant population persistence in fire-prone ecosystems. Here we evaluate the potential of this trait to respond to natural selection in its natural setting. For this we use a SNP-marker approach to estimate genetic variance and heritability of serotiny directly in the field for two Mediterranean pine species. Study populations were large and heterogeneous in climatic conditions and fire regime. We first estimated the realized relatedness among trees from genotypes, and then partitioned the phenotypic variance in serotiny using Bayesian animal models that incorporated environmental predictors. As expected, field heritability was smaller (around 0.10 for both species) than previous estimates under common garden conditions (0.20). An estimate on a subset of stands with more homogeneous environmental conditions was not different from that in the complete set of stands, suggesting that our models correctly captured the environmental variation at the spatial scale of the study. Our results highlight the importance of measuring quantitative genetic parameters in natural populations, where environmental heterogeneity is a critical aspect. The heritability of serotiny, although not high, combined with high phenotypic variance within populations, confirms the potential of this fire-related trait for evolutionary change in the wild.

火烧制度（fire regimes）与植物对火的适应性变异之间存在显著强关联，这表明植物会对作为选择因子的火做出快速响应，同时也提示与火相关的性状具有可遗传性——而可遗传性正是进化改变的必要前提。其中一个典型实例便是闭萌性（serotiny），即植物将种子储存在未开裂的果实或球果中，直至下一次火烧发生，这是火频发生态系统中植物种群维持存续的关键策略。本研究旨在评估该性状在自然生境中响应自然选择的潜力，为此我们采用单核苷酸多态性标记（SNP-marker）方法，直接在野外对两种地中海松的闭萌性性状开展遗传方差与遗传力估计。本次研究的种群规模较大，且其所处的气候条件与火烧制度均存在显著异质性，我们首先基于基因型数据估算个体间的实测亲缘关系（realized relatedness），随后利用纳入环境预测因子的贝叶斯动物模型（Bayesian animal models）对闭萌性的表型方差进行拆分。正如预期，野外实测得到的遗传力（两个物种均约为0.10）低于此前同质园实验（common garden）中的估计值（0.20）；对环境条件更均一的部分林分进行的子集分析所得遗传力估计结果，与全部林分的分析结果并无显著差异，这表明我们的模型已准确捕捉到研究空间尺度下的环境变异。本研究结果凸显了在自然种群中测定数量遗传参数的重要性——环境异质性是此类研究的关键考量因素，尽管闭萌性的遗传力并不高，但结合种群内较高的表型方差，证实了该火相关性状在野生环境中具备发生进化改变的潜力。