Big sagebrush (Artemisia tridentata) is a widespread and locally dominant shrub throughout many ecosystems in western North America. Three subspecies of big sagebrush have currently been identified: Artemisia tridentata subsp. tridentata, A. t. vaseyana, and A.t. wyomingensis. These subspecies occupy specific habitats. A.t. wyomingensis is commonly found in low elevation areas with dry soils, A.t. tridentata in intermediate elevation areas with intermediate soil moisture, and A.t. vaseyana in high elevation areas with wet soils. Differences in physiological functioning have been observed across subspecies of A. tridentata along an elevation gradient. However, it is unclear if these differences were due to genetic differences between the three subspecies or environmental factors. Furthermore, the potential for local adaptation, and the degree of phenotypic plasticity, is unknown in A. tridentata. Quantifying these is important for assessing the adaptive capacity of this widespread shrub.
Results/Conclusions
To tease apart genetic vs. environmental effects on ecophysiology, physiological measurements were conducted at the Orchard Common Garden located just outside of Boise, Idaho. These revealed no significant physiological differences based on subspecies. However, there were significant differences in gas exchange and hydraulic functional traits among populations. In addition, there was evidence of local adaptation, as photosynthesis and the ratio of photosynthesis-to-respiration declined with distance of the seed source from the common garden. These results suggest that at least some physiological traits exhibit plasticity. These findings are an important step towards understanding the adaptive abilities of big sagebrush (Artemisia tridentata). A better understanding of the physiological variation of the species could help aid in conservation and restoration projects in the future. These results show the need for further investigation of physiological different of this desert shrub, and the effects that their originating climate may have on them.