Response of clonal genotypes of Juncus effusus L. to different environmental regimes

A genetic tradeoff is hypothesized between resource use efficiency (RUE) and resource acquisition rate (RAR) in that it is impossible for selection to maximize both traits. In low-resource environments, RUE is expected to be favored while in high-resource environments RAR will be maximized. Growth rates and allocations of reciprocally transplanted clonal genotypes of J. effusus from differing nitrogen and elevation sites were examined. High-nitrogen populations outperformed their low-nitrogen counterparts, which were more nitrogen efficient. Plants originating from high-elevation sites grew larger irrespective of transplant environment. Elevation appears to be the dominant factor on biomass, nutrient allocation and growth at high elevation whereas nitrogen is the dominant factor in lower elevation. Minirhizotrons showed root growth was a function of origin site, with high-elevation populations outperforming others regardless of nitrogen treatment. Our results support the hypothesized negative correlation between the physiological traits for RUE and RAR.