Kin Selection in the Annual Plant Impatiens capensis

Kin selection occurs when phenotypic variation in a character or set of characters is heritable, spatially structured, and has differential fitness effects on neighboring individuals. Spatially structured, heritable variation has been found for many characters of the annual plant Impatiens capensis (the first two criteria). By manipulating plant growth by apical removal, I show that Impatiens fitness is strongly influenced by the phenotypes of neighboring plants, corroborating a previous study. A specific suite of phenotypes relating to plant architecture is consistently beneficial to neighboring plants. In addition, these manipulative experiments suggest that phenotypic plasticity may often impede purely observational field studies of kin selection in plant populations.