Ecology and Evolution of Photosynthetic Light Responses in the Hawaiian Lobelioids

夏威夷半边莲光合光反应的生态学和进化

• 批准号: 9904366
• 负责人: Thomas Givnish
• 金额: $ 42.8万
• 依托单位: University of Wisconsin-Madison
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-07-15 至 2003-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9904366&HistoricalAwards=false
• 关键词: Ecology; Evolution; Photosynthetic; Light; Responses

The Hawaiian lobelioids are one of the most spectacular examples of ecological diversification among plants. These woody plants occur in alpine bogs, dry sea cliffs, moist scrub, and tropical rainforest interiors and edges, and display a striking variety in growth form and leaf morphology. Based on the PIs' DNA family tree for this group, these plants appear to have invaded densely shaded habitats from the open, sunny sites they occupied before and shortly after their ancestors colonized Hawaii. The central aim of this project is to understand how plants acquire photosynthetic adaptations to sunny vs. shady conditions. The PIs will attempt to reconstruct changes in photosynthetic physiology, leaf form, biochemistry, and whole-plant growth that occurred when shady habitats were invaded from open sites. Species representing groups of related Hawaiian lobelioids, including species of relatively open habitats and closely related species that have more recently invaded deeper shade, will be studied. Field studies will be conducted to characterize the natural light environments of each study species and to measure their response in leaf form and photosynthesis to light availability under natural conditions. Greenhouse studies will be conducted to determine the extent to which different lobeliads show genetic differences in photosynthetic response, leaf traits, and whole-plant growth under different light regimes. Furthermore, these studies will reveal whether species of different habitats respond to variation in light in ways thought to be advantageous (e.g., do species of sunny habitats have photosynthetic rates and leaf traits that tend to increase growth in brightly lit environments at the cost of relatively poor growth in the shade (and vice versa for species of shaded habitats), and whether understory species - which inhabit a light environment that is patchy and relatively unpredictable - show more ability to alter their photosynthetic form and physiology in response to changed light conditions than species of more open habitats. When combined with information on the evolutionary relationships among the study species, this information will tell us what changes occurred at different stages in the invasion of shaded habitats, what characteristics appear to be adaptive to shady environments, and what characteristics appear to be constrained by the evolutionary history of the different groups.This research will allow the PIs to investigate, for the first time, the rise of photosynthetic adaptations to sun vs. shade in a historical framework. The results should increase our understanding of the ecological constraints on photosynthetic performance in plants generally, and of the habitat requirements for lobelioids specifically, many species of which have become quite rare.

夏威夷水母是植物中生态多样化的最引人注目的例子之一。这些木本植物生长在高山沼泽，干燥的海崖，潮湿的灌木丛和热带雨林的内部和边缘，并在生长形式和叶形态上显示出惊人的多样性。根据PI对这一群体的DNA谱系树，这些植物似乎从它们的祖先殖民夏威夷之前和之后不久占据的开阔、阳光充足的地方入侵了稠密遮蔽的栖息地。这个项目的中心目标是了解植物如何获得对晴朗和阴凉条件的光合作用适应。PI将尝试重建当树荫栖息地从开阔的地点入侵时发生的光合作用生理、叶片形状、生物化学和全植物生长的变化。代表夏威夷近缘类的物种，包括相对开放的栖息地物种和最近入侵较深阴凉处的密切相关物种，将被研究。将进行实地研究，以确定每个研究物种的自然光环境特征，并测量它们在自然条件下的叶形和光合作用对光可获得性的反应。将进行温室研究，以确定不同的半边莲在不同的光照条件下，在光合作用反应、叶片特征和全株生长方面表现出遗传差异的程度。此外，这些研究将揭示不同生境的物种是否以被认为是有利的方式对光的变化作出反应(例如，阳光充足的生境的物种是否具有倾向于在明亮的光照环境中促进生长的光合作用和叶片特征，而代价是在阴凉的环境中生长相对较差)，以及林下物种--居住在零星和相对不可预测的光环境中--是否比更开放的生境的物种显示出更强的能力来改变其光合作用形式和生理，以应对变化的光照条件。结合研究物种间进化关系的信息，这些信息将告诉我们在遮荫生境入侵的不同阶段发生了哪些变化，哪些特征似乎适应了阴暗环境，以及哪些特征似乎受到不同物种进化历史的限制。这项研究将使PI能够首次在历史框架内调查光合作用对日照和遮荫的适应程度的上升。这些结果应该会增加我们对植物光合作用表现的生态限制的理解，特别是对许多已经变得相当稀有的扇贝类植物的栖息地要求的理解。