Adaptation of Senecio vulgaris (Asteraceae) to ruderal and agricultural habitats

Adaptation of the annual plant Senecio vulgaris to ruderal and agricultural habitats was investigated. We expected S. vulgaris to be adapted to the ag ricultural habitat through nutrient-specific differentiation of relatively few genotypes responding to the generally high homogenous nutrient levels a t the agricultural habitat caused by constant fertilization. To assess adap tation of S. vulgaris, vegetative and reproductive responses of seed famili es from various populations of agricultural and ruderal habitats, grown in the greenhouse at high and low nutrient levels, were compared. Data were an alyzed with a three-level nested ANOVA based on the levels habitat, populat ion, and family. A significant habitat effect indicated that S. vulgaris fr om ruderal and agricultural habitats were genetically different with plants from the agricultural habitat having larger leaves and a higher reproducti on. A significant habitat by nutrient effect showed a stronger response of reproduction to nutrients at the agricultural habitat, suggesting that gene tic differentiation among habitats is nutrient-specific. Contrary to expect ations, only the agricultural habitat showed genetic diversity of S. vulgar is. Results suggest that nutrient levels at the agricultural habitat are mo re heterogeneous as generally proposed leading to a relatively high genetic variation.