Synergistic Effects of Light and Water on Physiological Diversification in the Hawaiian Llobeliads

夏威夷半边莲（桔梗科）是开花植物适应辐射的最壮观的例子之一，从完全开放到密集的阴影微型站点，年降雨量从500到12，000毫米。先前的研究提供了一个分子系统学为这个分支，记录了分布的11个代表性的物种沿着梯度的光子通量密度（PFD），并证明了适应PFD的静态和动态光合光响应和相关的叶片性状通过现场和普通花园的研究。栖息地的多样化通常伴随着光合生理的变化，遵循经典的阳光与阴影适应模式。然而，光的可用性几乎不可避免地与降雨量和蒸发需求的变化相关，后者受阳光与阴凉微型站点的空气温度，相对湿度和热负荷差异的影响。因此，目前还不清楚-在夏威夷半边莲，或整个陆地植物-光合反应和相关的叶性状的变化，沿着PFD梯度反映适应变化的程度在光本身，水分供应相对于需求，或两者兼而有之。初步数据表明，光和水分的可用性相互作用，以塑造光合光响应和相关的叶性状在半边莲原产于不同的栖息地。该研究测试的假设，即水与光的可用性的相互作用，严重影响了几个夏威夷半边莲适应一系列的光和水分梯度的生理多样化和适应性进化的路径。实验将描述田间条件下的水分关系，包括研究叶水势、气孔对湿度的反应、光合作用对VPD的反应、叶水力传导率和水力脆弱性。 在一个共同的花园实验将被用来分析水的关系，水力学，光合作用，相关的叶性状，并在常见条件下整个植物生长的生态和进化的变化。 最后，研究将确定在夏威夷群岛广泛的环境梯度中是否会出现生理特征的进化趋势。研究结果将提供基本的见解，在陆地植物的气体交换策略的演变。通过在明确的亲缘关系的背景下对密切相关的类群进行这种研究，将得出关于各种性状的进化途径以及生态与祖先在塑造当今物种特征中的作用的重要推论。外联活动包括为欧空局的生态学教学问题和实验开发一个模块;与火山艺术和科学学院以及Kamehameha学校Kea 'Au校区协调，为K-8学生开发一个关于当地植物适应的模块;通过与UH-Hilo REU方案欧空局SEEDS方案协调，为代表性不足群体的本科生提供夏季研究机会。

The Hawaiian lobeliads (Campanulaceae) are one of the most spectacular examples of adaptive radiation in flowering plants, ranging from fully open to densely shaded microsites and from 500 to 12,000 mm annual rainfall. Prior research has provided a molecular phylogeny for this clade, documented the distribution of 11 representative species along a gradient of photon flux density (PFD), and demonstrated the adaptation to PFD of static and dynamic photosynthetic light responses and associated leaf traits via field and common-garden studies. Diversification in habitat has generally been accompanied by shifts in photosynthetic physiology that follow classic patterns of adaptation to sun vs. shade. However, light availability is almost inevitably correlated with variation in rainfall and evaporative demand, with the latter affected by differences in air temperature, relative humidity, and heat load in sunny vs. shady microsites. It is thus unclear - in Hawaiian lobeliads, or across land plants - the extent to which variation in photosynthetic responses and associated leaf traits along PFD gradients reflects adaptation to variation in light per se, moisture supply relative to demand, or both. Preliminary data suggest that light and moisture availability interact to shape photosynthetic light responses and associated leaf traits in lobeliads native to different habitats. The research tests the hypothesis that the interaction of water with light availability critically influenced the path of physiological diversification and adaptive evolution in several Hawaiian lobeliads adapted to a range of light and moisture gradients. Experiments will characterize water relations under field conditions, including studies of leaf water potential, stomatal response to humidity, photosynthetic response to VPD, leaf hydraulic conductance and hydraulic vulnerability. Experiments in a common garden will be used to analyze ecological and evolutionary shifts in water relations, hydraulics, photosynthesis, associated leaf traits, and whole plant growth under common conditions. Finally, research will determine if evolutionary trends occur in physiological traits across broad environmental gradients in the Hawaiian Islands. Findings will provide fundamental insights into the evolution of gas exchange strategies in land plants. By conducting such studies on closely related taxa in the context of an explicit phylogeny, important inferences will be drawn about evolutionary pathways for various traits, and the role of ecology vs. ancestry in shaping the characteristics of present-day species. Outreach activities include developing a module for the ESA's Teaching Issues and Experiments in Ecology; coordinating with the Volcano School of Arts and Sciences, and Kamehameha Schools Kea`au campus to develop a module on local plant adaptation for K-8 students; and providing summer research opportunities for undergraduate students from underrepresented groups through coordination with the UH-Hilo REU program & ESA SEEDS program.