Merino Gabriel, Ramírez-Barahona Santiago, Olson Mark E, Núñez-Farfán Juan, García-Oliva Felipe, Eguiarte Luis E
Departamento de Ecología Evolutiva, Instituto de Ecología, Universidad Nacional Autónoma de México, Mexico City, Mexico.
Posgrado en Ciencias Biológicas, Universidad Nacional Autónoma de México, Unidad de Posgrado, Ciudad Universitaria, Coyoacán, Mexico City, Mexico.
PLoS One. 2023 Sep 27;18(9):e0291945. doi: 10.1371/journal.pone.0291945. eCollection 2023.
Knowing how species and communities respond to environmental change is fundamental in the context of climate change. The search for patterns of abundance and phenotypic variation along altitudinal gradients can provide evidence on adaptive limits. We evaluated the species abundance and the variation in morphometric and stomatal characters in five tree ferns species (Cyathea fulva, C. divergens, C. myosuroides, Alsophila firma and Gymnosphaera salvinii) distributed along an elevation gradient in a well-preserved Mexican cloud forest. Variation at the community and species level was assessed using exploratory and multivariate data analysis methods. We wanted to explore if the species abundance is environmentally determined, to determine the degree of variation along the elevation gradient, to test for differences between zones and associations with elevation, humidity and soil nutrients, and to assess contribution of the intra- and interspecific variation to the community response to elevation and soil nutrients. The studied fern community showed strong species turnover along the elevation gradient, with some influence of soil nutrient concentration, supporting environmental determinism. All measured characters displayed variation along the gradient. Stomatal characters (size and density) had significantly less variation than morphometric characters (trunk diameter, stipe length and blade length), but stomatal density also shows interesting intraspecific patterns. In general, patterns within the fern community suggest a strong influence of species identity, especially of species inhabiting the lower edge of the cloud forest, which showed the clearest morphometric and stomatal patterns, associated to contrasting environments rather than to changes in elevation. The coincidence between morphometric and stomatal patterns in this area suggest hydraulic adjustments in response to contrasting environments. Our results provide evidence that tree ferns species respond to environmental changes through adjustments of morphometric plasticity and stomatal density, which is relevant to predict possible responses to variation in environmental conditions resulting from climate change.
了解物种和群落如何应对环境变化是气候变化背景下的基础。探寻沿海拔梯度的丰度模式和表型变异可为适应性极限提供证据。我们评估了分布在墨西哥一片保存完好的云雾森林海拔梯度上的五种树蕨物种（富氏桫椤、歧裂桫椤、鼠尾桫椤、黑桫椤和萨尔文桫椤）的物种丰度以及形态特征和气孔特征的变异。使用探索性和多变量数据分析方法评估了群落和物种水平的变异。我们想探究物种丰度是否由环境决定，确定沿海拔梯度的变异程度，测试不同区域之间的差异以及与海拔、湿度和土壤养分的关联，并评估种内和种间变异对群落对海拔和土壤养分响应的贡献。所研究的蕨类群落沿海拔梯度显示出强烈的物种更替，受土壤养分浓度的一定影响，支持环境决定论。所有测量特征均沿梯度显示出变异。气孔特征（大小和密度）的变异明显小于形态特征（树干直径、叶柄长度和叶片长度），但气孔密度也呈现出有趣的种内模式。总体而言，蕨类群落中的模式表明物种身份有很强的影响，尤其是栖息在云雾森林下缘的物种，它们表现出最清晰的形态和气孔模式，与对比鲜明的环境相关，而非与海拔变化相关。该区域形态和气孔模式的巧合表明存在针对对比鲜明环境的水力调节。我们的结果提供了证据，表明树蕨物种通过形态可塑性和气孔密度的调节来应对环境变化，这对于预测气候变化导致的环境条件变化可能产生的响应具有重要意义。
