Performance of reciprocally sown populations of Senecio vulgaris from ruderal and agricultural habitats

Senecio vulgaris from ruderal habitats may colonise crop fields and persist in the new environment. Persistence may occur through phenotypic plasticit y or genetic differentiation. In the presence of genetic variation. differe ntial responses of life history traits to selection may lead to local adapt ation. A reciprocal seed transplant experiment was conducted to determine e nvironmental and genetic variation of life history traits in S. vulgaris fr om ruderal and agricultural habitats, and whether infection by the rust Puc cinia lagenophorae is a selection factor in S. vulgaris populations. Emerge nce, growth and fecundity showed environmental as well as genetic variation , as shown by a significant site and origin effect. However. there was no e vidence of local adaptation, as indicated by the absence of significant ori gin by site interactions. Genetic variation in emerging seedling numbers se ems to be important for S. vulgaris, an annual plant which has no means oth er than seed production for propagation. Seedling survival was solely under environmental control stressing the importance of stochastic events for pl ant mortality, Most S. vulgaris from ruderal sites showed reduced growth. b ut still reached reproduction, suggesting that S. vulgaris is following the plastic strategy of a stress tolerator to endure unfavourable environments . Plants at most agricultural sites behaved like r-strategists, exploiting a productive environment for rapid plant growth and maximising reproduction . Emergence, survival, growth and fecundity were higher at the agricultural sites. Infection by the rust occurred at all sites. with the highest incid ence at the agricultural sites. and was solely determined by the environmen t. A higher incidence did not result in an increased disease impact on plan t growth and reproduction nor did it affect survival of S. vulgaris. Althou gh the majority of life-history traits studied showed phenotypic and geneti c variation, which can both be subject to natural selection, no adaptation of S. vulgaris to its local environment was detected.