- Plasticity and constancy in plant functional traits may relate to optimal strategies at the respective habitat and to ecotypic differentiation along elevation.
- We examined soil N availability in the field and conducted a growth analysis for two elevational ecotypes of Arabidopsis halleri grown under different nutrient availabilities to evaluate phenotypic plasticity and optimal biomass allocation.
- Soil N availability increased rather than decreased with increasing elevation. The highland ecotype was more plastic in physiological variables, whereas lowland ecotype was more plastic in morphological variables and N concentrations. The leaf mass ratio (LMR) in the lowland ecotype was moderately plastic at the whole range of studied N availabilities, whereas LMR in the highland ecotype was very plastic at higher N availabilities but not at lower N availabilities. An optimality model indicated that LMR of the lowland ecotype was nearly optimal at the whole range of studied N availability, whereas that of the highland ecotype was suboptimal at the low N availability.
- Our results suggest that the highland ecotype is adapted only to high N availabilities, whereas the lowland ecotype is adapted to relatively wide range of N availability as a result of natural selection in their respective habitats.