title: Population divergence along lines of genetic variance and covariance in the invasive plant Lythrum salicaria in eastern North America.
abstract: 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.
authors: Department of Ecology & Evolutionary Biology, University of Toronto, 25 Willcocks St. Toronto, Ontario M5S 3B2, Canada. rob.colautti@utoronto.ca
authors: Robert I
authors: RI
authors: Colautti
authors: Spencer C H
authors: SC
authors: Barrett
mesh_terms: D000222:Adaptation, Physiological; D005075:Biological Evolution; D002980:Climate; D056084:Genetic Fitness; D014644:Genetic Variation; D058865:Introduced Species; D031561:Lythrum / Q000235:genetics* / Q000254:growth & development*; D009864:Ontario; D010641:Phenotype; D012098:Reproduction; D013997:Time Factors; D014481:United States