Data.xls

The outcome of interspecific competition is affected by numerous abiotic and biotic factors. Here we demonstrate an aspect of interspecific competition: the genotype of a conspecific neighbour determines the outcome of interspecific competition through phenotypic plasticity in a perennial plant, Plantago asiatica. We investigated effects of the genotype of neighbour sibling or non-sibling P. asiatica plants on competition with Trifolium repens plants when Plantago plants were separated above or below ground from T. repens, separated below ground from each other or not separated. Seed production of P. asiatica individuals was negatively correlated with biomass of Trifolium repens. Sibling but not non-sibling pairs of P. asiatica plants increased leaf placement in the direction of T. repens plants, which was negatively correlated with biomass of T. repens and positively correlated with seed production of P. asiatica. Seed production of P. asiatica plants competing with T. repens was greater in individuals paired with siblings than in those paired with non-. siblings These results support the hypothesis that the genetic spatial structure within a species influences outcomes of interspecific competition through genetic-structure-dependent plasticity.