Data from: Population divergence along lines of genetic variance and covariance in the invasive plant Lythrum salicaria in eastern North America

Evolution during biological invasion may occur over contemporary timescales, but the rate of evolutionary change may be inhibited by a lack of standing genetic variation for ecologically relevant traits and by fitness trade-offs among them. The extent to which these genetic constraints limit the evolution of local adaptation during biological invasion has rarely been examined. To investigate genetic constraints on life-history traits, we measured standing genetic variance and covariance in 20 populations of the invasive plant purple loosestrife (Lythrum salicaria) sampled along a latitudinal climatic gradient in eastern North America and grown under uniform conditions in a glasshouse. Genetic variances within and among populations were significant for all traits; however, strong intercorrelations among measurements of seedling growth rate, time to reproductive maturity and adult size suggested that fitness trade-offs have constrained population divergence. Evidence to support this hypothesis was obtained from the genetic variance–covariance matrix (G) and the matrix of (co)variance among population means (D), which were 79.8% (95% C.I. 77.7–82.9%) similar. These results suggest that population divergence during invasive spread of L. salicaria in eastern North America has been constrained by strong genetic correlations among life-history traits, despite large amounts of standing genetic variation for individual traits.生物入侵进程中的演化可在当代时间尺度上发生，但演化变化的速率可能受到两方面限制：一是生态相关性状缺乏现存遗传变异，二是这些性状间存在适合度权衡。目前鲜有研究探讨这些遗传限制在生物入侵过程中对本地适应演化的限制程度。为探究生活史性状受到的遗传限制，我们针对北美东部沿纬度气候梯度取样的20个入侵植物千屈菜（Lythrum salicaria）种群，在温室统一栽培条件下测定了其现存遗传方差与协方差。所有性状的种群内和种群间遗传方差均显著；然而，幼苗生长速率、生殖成熟时间与成体体型的测定指标间存在强相关性，这表明适合度权衡限制了种群分化。我们从遗传方差-协方差矩阵（G矩阵）与种群均值间（协）方差矩阵（D矩阵）中获得了支持该假说的证据，二者的相似度达79.8%（95%置信区间：77.7%–82.9%）。这些结果表明，尽管千屈菜在北美东部入侵扩散过程中各生活史性状均存在大量现存遗传变异，但其种群分化仍受到生活史性状间强遗传相关性的限制。