Convergent Evolution and Ecophysiological Differentiation in Chaparral Shrubs: A Comparative Analysis

加利福尼亚灌木林和世界各地类似的群落在植物生态学的发展中发挥了关键作用。这些群落中远亲物种的生态相似性长期以来一直是趋同适应的典型例子。此外，物种间生态差异的研究在阐明与非生物胁迫和干扰相关的替代策略方面发挥了核心作用。生态变异的研究主要集中在两个方面：1)与生根深度和生境分布有关的水分关系和耐旱性；2)与火灾后再生有关的生活史策略对比。本研究的第一个目的是通过对加利福尼亚北部到南部三个地点的30多个物种进行广泛的比较研究，研究光合特性、耐旱性和火再生特性之间的关系。该项目的第二个目标是将这些生态学研究与快速发展的植物物种间系统发育关系的知识结合起来，以测试这些物种之间的相似性和差异性是否代表了对灌木林气候的局部适应，或者是导致当前群落聚集的更古老的特征。该项目首次尝试评估大量生理和生活史性状对木本植物功能群鉴定的贡献。功能基团的鉴定是了解不同植物群落共存机制和评估不同物种对变化的火灾和其他环境条件的潜在反应的关键步骤。此外，该项目将最终为长期存在的灌木状社区趋同适应范式提供测试。

The California chaparral and similar communities around the world have played a pivotal role in the development of plant ecology as a science. The ecological similarity of distantly related species in these communities has long served as a paradigmatic example of convergent adaptation. In addition, the study of ecological differences between species has played a central role in elucidating alternative strategies related to abiotic stress and disturbance. The study of ecological variation has focused on two features: i) water relations and drought tolerance, in relation to rooting depth and habitat distribution, and ii) contrasting life history strategies related to regeneration following fire. The first objective of this study is to examine the relationships between photosynthetic characteristics, drought tolerance, and fire-regeneration traits in a broad comparative study of over 30 species from three sites ranging from northern to southern California. The second objective of this project is to integrate these ecological studies with the rapidly expanding knowledge of phylogenetic relationships among plant species to test whether the similarities and differences among these species represent local adaptations to the chaparral climate, or older characteristics which then led to the assembly of the current community. This project represents the first attempt to assess the contributions of a large number of physiological and life-history traits to the identification of functional groups in woody plant species. The identification of functional groups is a critical step in understanding the mechanisms of coexistence in diverse plant communities, and in assessing the potential responses of different species to changing fire regimes and other environmental conditions. Furthermore, this project will finally provide a test of the long-standing paradigm of convergent adaptation in chaparral-like communities.