Tracking leaf trait differentiation of newly diverging subspecies of Chenopodium oahuense on the Hawaiian Islands

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Myriam Serrano, Jason T. Cantley and Kevin A. Simonin, Department of Biology, San Francisco State University, San Francisco, CA

Background/Question/Methods
A single native Chenopodium species, Chenopodium oahuense, can be found throughout the Hawaiian archipelago. Subpopulations of this species can be found in a wide range of habitats that differ greatly in temperature, humidity and elevation. Field observations and experiments in common gardens suggest that large climate differences across the population range are driving distinct morphologies. These morphological differences are likely associated with physiological adaptations to the local climates of the subpopulations; however, physiological comparisons have not been done. By utilizing a common garden, we will compare previously observed differences in gross plant structure with functional differences in whole plant water use strategies and coupled to an environmental niche model based on data from GBIF, iDigBio, and field surveys. Our main objective is to document Chenopodium oahuense leaf traits (e.g. leaf size, stomatal density, leaf hydraulic conductance, osmotic potential at full turgor and leaf level capacitance) for the different sub-populations and between juvenile and adult growth forms. We also intend to elucidate how variation in each sub population’s home environment has led to adaptive shifts in plant water use strategies.
Results/Conclusions
Preliminary results suggest that the environmental niche differences such as elevation, rainfall, and annual temperature experienced by each subpopulation are strongly coupled to differences in water use strategy. Pressure volume curve analyses of the different subpopulations are showing differences in osmotic potential at full turgor and turgor loss point. Preliminary stomatal conductance and leaf size measurements also indicate differences between juveniles and adults within populations. In conclusion our preliminary data suggest differences in plant water use strategy are linked to the population’s distinct environmental conditions. Increasing our understanding of diversification and evolutionary adaptations within a specific lineage has broad implications for understanding other ecological systems with diverging sub populations. We will also be able to make informed conservation decisions for C. oahuense that will, in turn, impact the conservation of other organisms that rely on them.