Physiology, Phylogeny and Adaptation in Schiedea (Caryophyllaceae): An Endemic Hawaiian Plant Genus

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9601325 Dawson This research is an investigation of patterns of functional diversity with respect to their phylogenetic (evolutionary) relationships within Schiedea (Caryophyllaceae). A phylogeny (evolutionary tree) of the genera Schiedea and Alsinidendron shows that the two genera arose from the same ancestor and have radiated into diverse habitats in the Hawaiian Islands, and include rain forest vines, coastal and subalpine shrubs, and herbs. The comparative ecology and physiology of plants has rarely been conducted in a rigorous phylogenetic context, with knowledge of the evolutionary relationships of the species. As a result, it is difficult to know whether physiological, anatomical and morphological traits are adaptations to different environments because these traits have changed through evolutionary time in response to novel selection in new habitats or are historical artifacts of past selection. This research will study patterns of physiological specialization associated with shifts in breeding system and morphology that accompany shifts in habitat preference. Research objectives are: (1) to describe the patterns of physiological diversity (patterns of water use and water-use efficiency using measurements of carbon fixation and water loss rates, instantaneous water use efficiency, carbon isotope ratio, hydraulic properties, and their associated morphological changes) for 9 representative species; (2) analyze habitat characteristics and correlate them with the functional traits for these species; (3) interpret functional characteristics with respect to their evolutionary relationships to understand patterns of physiological and morphological character evolution; and (4) provide a detailed analysis of functional changes within species and by gender that have occurred as hermaphroditic species colonized drier habitats and different breeding systems evolved. Field studies will provide information about functional variation under natural conditions, and common garden studies will pr ovide information about functional variation among species and by gender under controlled conditions in the absence of environmental variation. In particular, plant hydraulic architecture (e.g., wood structure and water transport properties) is likely to have contributed to enhanced drought tolerance for Schiedea with evolution of woody features and colonization of drier habitats. This study is one of the first to merge plant physiological ecology with phylogenetic systematics, and permits an understanding of the nature and patterns of physiological and functional character evolution. Greater knowledge of how physiological and other functional characters change through evolutionary time with changes in environment is critical to understand how global climate changes will affect both native and agricultural plants.