Outcome of interspecific competition depends on genotype of conspecific neighbours

The outcome of interspecific competition is affected by numerous abiotic and biotic factors. However, the effects of genetic relatedness of conspecific neighbours have not been elucidated. Here, we demonstrate that the genotype of a conspecific neighbour determines the outcome of interspecific competition. We investigated effects of genotype of neighbour sibling or non-siblingPlantago asiaticaplants on competition withTrifolium repensplants. Pairs ofP. asiatica, sibling or non-sibling, were grown in competition withT. repens. SiblingP. asiaticaplants, but not non-sibling plants, increased leaf placement towards competitorT. repensplants, and that placement was correlated negatively with the biomass ofT. repensand positively with seed production byP. asiatica. Seed production byP. asiaticaplants competing withT. repenswas greater in individuals paired with siblings than in those paired with non-siblings. Thus, our results show that the genotype of conspecific neighbours can alter the outcome of interspecific competition.