Phenotypic plasticity and specialization along an altitudinal gradient in Trifolium repens

Phenotypic plasticity and specialization represent seemingly contrasting strategies to heterogeneous environments. Specialization is associated with the loss of phenotypic plasticity, particularly in functional traits. However, it is equivocal if this loss of plasticity is observed only in the specific habitat and stress type where the specialization occurs or a general loss of plasticity is seen across habitats. We examined populations of Trifolium repens L. following an expansion during the colonization of Australia from relatively good low altitude habitats to more stressful high altitude habitats in the Blue Mountains region, New South Wales, Australia. We examined if specialization to abiotic stress causes a loss of adaptive plasticity in functional traits under competition treatments (a different type of stress rather than abiotic stress). We found that both low and high altitude populations experienced a loss in performance in competition treatments and did not express a shade avoidance response under competition. Specialization to higher abiotic stress was associated with the loss of adaptive plasticity in functional traits. Our results suggest that specialization may limit the responses of plants to future environmental changes.