Within-population variation in demography of Taraxacum officinale: Maintenance of genetic diversity

Differential response of genotypes to temporal environmental heterogeneity may contribute to the long-term persistence of those genotypes within a population. We tested whether season-dependent fitness components of genotypes could be responsible for the maintenance of genetic diversity within a population. Clonal replicates of five genotypes of Taraxacum officinale were planted in each of four seasons (spring-April to July, summer-July to October, autumn-October to January, and winter-January to April), Individuals were planted directly into natural, field vegetation. Fitness components (establishment, survival, growth, seed production, and leaf area dominance) and an integrated measure of fitness (finite rate of increase) were measured for each genotype in each season. Differential genotypic responses to seasons were observed for all fitness components. Despite seasonal differences, genotypic performances summed across seasons were equivalent. This result indicates that temporal heterogeneity may have a substantial effect on within-population genetic structure. The persistence of genotypes of contrasting seasonal performance through time is expected if long-term fitness values remain similar.