The costs and benefits of tolerance to competition in Ipomoea purpurea, the common morning glory

Tolerance to competition has been hypothesized to reduce the negative impact of plant-plant competition on fitness. Although competitive interactions are a strong selective force, an analysis of net selection on tolerance to competition is absent in the literature. Using fifty-five full/half-sibling families from 18 maternal lines in the crop weed Ipomoea purpurea we measured fitness and putative tolerance traits when grown with and without competition in an agricultural field. We tested for the presence of genetic variation for tolerance to competition and determined if there were costs and benefits of this trait. We also assessed correlations between tolerance and potential tolerance traits. We uncovered a fitness benefit of tolerance in the presence of competition and a cost in its absence. We failed to detect evidence of additive genetic variation underlying tolerance, but did uncover the presence of a significant maternal line effect for tolerance, which suggests its evolutionary t...