An invasive plant alters phenotypic selection on the vegetative growth of a native congener.

PREMISE OF THE STUDY The ecological consequences of plant competition have frequently been tested, but the evolutionary outcomes of these interactions have gone largely unexplored. The study of species invasions can make an important contribution to this field of research by allowing us to watch ecological and evolutionary processes unfold as a novel species is integrated into a plant community. We explored the ecological and evolutionary impact of an invasive jewelweed, Impatiens glandulifera, on a closely related native congener, I. capensis and asked: (1) Does the presence of the invasive jewelweed alter the fitness of native jewelweed populations? (2) Does the invasive jewelweed affect the vegetative growth of the native congener? and (3) Does the invasive jewelweed alter phenotypic selection on the vegetative traits of the native congener? METHODS We used a greenhouse competition experiment, an invasive species removal field experiment, and a survey of natural populations. KEY RESULTS We show that when the invasive jewelweed is present, phenotypic selection favors native jewelweed individuals investing less in rapid upward growth and more in branching and fruiting potential through the production of nodes. CONCLUSIONS This research demonstrates that invasive plants have the potential to greatly alter natural selection on native competitors. Studies investigating altered selection in invaded communities can reveal the potential evolutionary impact of invasive competitors, while deepening our understanding of the more general role of competition in driving plant evolution and permitting species coexistence.