Data from: 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 trajectory is not easily predicted. The cost of tolerance is likely due to later initiation of flowering of tolerant individuals in the absence of competition, whereas relative growth rate was found to positively covary with tolerance in the presence of competition, and can thus be considered a tolerance trait.已有假说提出，竞争耐受性（tolerance to competition）可降低植株间竞争对植物适合度的负面影响。尽管竞争互作是强有力的选择压力，但目前学界尚未有针对竞争耐受性的净选择效应开展的系统分析研究。本研究以农田杂草圆叶牵牛（Ipomoea purpurea）18个母系株系衍生的55个全同胞/半同胞家系为实验材料，在农田生境中设置有竞争与无竞争两种栽培处理，测定了植株的适合度及潜在耐受性相关性状。本研究旨在检验竞争耐受性是否存在遗传变异，并明确该性状是否存在适合度代价与收益；同时分析了竞争耐受性与潜在耐受性相关性状之间的相关性。研究结果显示，在存在竞争的环境中，竞争耐受性可带来显著的适合度收益；而在无竞争环境下，该性状则存在适合度代价。本研究未检测到竞争耐受性背后存在加性遗传变异的证据，但却发现竞争耐受性存在显著的母系株系效应，这表明该性状的演化轨迹难以被精准预测。竞争耐受性的适合度代价可能源于无竞争环境下耐受性个体的开花启动时间晚于非耐受性个体；而在存在竞争的环境中，相对生长速率与竞争耐受性呈正相关，因此可被认定为一项耐受性相关性状。