Previous studies have identified trade-offs in suites of functional traits associated with adaptation to mesic or xeric environments. Specifically, we predict that species growing in mesic environments should have higher hydraulic conductance, photosynthetic capacity, and growth rates, while species in xeric habitats will adopt more conservative strategies of resource use reflected in higher water-use efficiency and resistance to embolism.

For each of the three species pairs (1. Dubautia menziesii and Dubautia reticulata; 2. Dubautia arborea and Dubautia ciliolata; 3. W. gymnoxiphium and Dubautia raillardioides) we will conduct field and greenhouse studies to determine:

• the divergence of traits adaptive to mesic or xeric environments
• correlations and trade-offs among traits (growth, morphological, anatomical and physiological traits) associated with a given environment.
• the degree to which phenotypic plasticity is responsible for observed variation in traits

For each species, one naturally-distributed population will be studied in the Hawaiian islands and one greenhouse population (20 plants) will be studied in the greenhouse at Clemson University. Environmental variation will be monitored at each target site using micrometeorological stations. Each of the three sites will be visited twice per year for seven to ten days, early in the growing season (April – May) and in the again in the summer (July – August) to evaluate the response functional traits to the range of environment variation at each site. Because of their monocarpic habit, populations of Wilkesia gymnoxiphium will be grown on Kauai at the National Tropical Botanic Garden under the supervision.