Pilote Alex J, Donovan Lisa A
Department of Plant Biology, University of Georgia, Athens, Georgia 30602 USA
Department of Plant Biology, University of Georgia, Athens, Georgia 30602 USA.
Am J Bot. 2016 Dec;103(12):2096-2104. doi: 10.3732/ajb.1600314. Epub 2016 Dec 13.
Patterns of plant stem traits are expected to align with a "fast-slow" plant economic spectrum across taxa. Although broad patterns support such tradeoffs in field studies, tests of hypothesized correlated trait evolution and adaptive differentiation are more robust when taxa relatedness and environment are taken into consideration. Here we test for correlated evolution of stem and leaf traits and their adaptive differentiation across environments in the herbaceous genus, Helianthus.
Stem and leaf traits of 14 species of Helianthus (28 populations) were assessed in a common garden greenhouse study. Phylogenetically independent contrasts were used to test for evidence of correlated evolution of stem hydraulic and biomechanical properties, correlated evolution of stem and leaf traits, and adaptive differentiation associated with source habitat environments.
Among stem traits, there was evidence for correlated evolution of some hydraulic and biomechanical properties, supporting an expected tradeoff between stem theoretical hydraulic efficiency and resistance to bending stress. Population differentiation for suites of stem and leaf traits was found to be consistent with a "fast-slow" resource-use axis for traits related to water transport and use. Associations of population traits with source habitat characteristics supported repeated evolution of a resource-acquisitive "drought-escape" strategy in arid environments.
This study provides evidence of correlated evolution of stem and leaf traits consistent with the fast-slow spectrum of trait combinations related to water transport and use along the stem-to-leaf pathway. Correlations of traits with source habitat characteristics further indicate that the correlated evolution is associated, at least in part, with adaptive differentiation of Helianthus populations among native habitats differing in climate.
植物茎干性状模式预计会与跨分类群的“快-慢”植物经济谱相一致。尽管在实地研究中广泛的模式支持这种权衡，但在考虑分类群亲缘关系和环境时，对假设的相关性状进化和适应性分化的测试会更加可靠。在这里，我们测试了草本植物向日葵属中茎和叶性状的相关进化及其在不同环境中的适应性分化。
在一个共同花园温室研究中评估了14种向日葵（28个种群）的茎和叶性状。系统发育独立对比用于测试茎干水力和生物力学特性相关进化的证据、茎和叶性状的相关进化以及与源栖息地环境相关的适应性分化。
在茎干性状中，有证据表明一些水力和生物力学特性存在相关进化，支持了茎干理论水力效率与抗弯曲应力之间预期的权衡。发现茎和叶性状组合的种群分化与与水分运输和利用相关的性状的“快-慢”资源利用轴一致。种群性状与源栖息地特征的关联支持了干旱环境中资源获取型“干旱逃避”策略的反复进化。
本研究提供了茎和叶性状相关进化的证据，这与沿茎到叶途径与水分运输和利用相关的性状组合的快-慢谱一致。性状与源栖息地特征的相关性进一步表明，这种相关进化至少部分与向日葵种群在气候不同的原生栖息地之间的适应性分化有关。
