Abstract
Qualitative and quantitative studies of the pattern of invasive plant development is now considered a key aspect in understanding invasiveness. This work was performed to determine relationships between shrub architectural plasticity and proliferating behaviour. We selected five shrub species (Cornus sericea L., Cornaceae ; Prunus virginiana L., Rosaceae ; Rhamnus cathartica L., Rhamnaceae ; Rhus typhina L., Anacardiaceae ; Zanthoxylum americanum Mill., Rutaceae) known to arrest plant succession under certain conditions in Southern Québec, Canada. Architectural analysis revealed species' structural units and their ontogenic changes. These ontogenic changes need to be calibrated if a full description of phenotypic plasticity is to be obtained. Analysis of the plant structural units reveals that they are of different functional significance: the higher the level of organization, the greater the capacity for phenotypic plasticity and competition. We defined three architectural strategies related to individual behaviours and which can relevantly explain the population proliferation of shrubs.