GENETIC DIFFERENTIATION BETWEEN POPULATIONS OF PLANTAGO-LANCEOLATA .2. PHENOTYPIC SELECTION IN A TRANSPLANT EXPERIMENT IN 3 CONTRASTING HABITATS

(1) Populations of Plantago lanceolata were grown in a reciprocal-transplant experiment in an early-mown hayfield, a wet, late-mown hayfield and a pasture. At all three sites, populations and clones differed significantly in components of seed yield such as survival, incidence of flowering and seed set, and in annual seed yield. (2) Components of seed yield of transplants were correlated with the height of the surrounding vegetation. In the pasture, plants produced far more seeds in tall vegetation, which was probably due to a low local grazing intensity. In contrast, in the early-mown hayfield tall vegetation was associated with a lower lifetime seed yield. At all three sites, tall vegetation coincided with a low survival of transplants. (3) In the early-mown hayfield selection on timing of flowering and growth habit was found, which agreed with the expectations from the observed differences between populations. At all sites seed production varied above all because of differences in plant size, and no further direct effects of phenotypic traits on seed yield could be detected. (4) Specialization of clones to certain sites was tested by calculating correlations of seed-yield components across sites. No significant correlations were found between components of seed yield per clone across sites. This was probably due to the positive correlation of the mean plant size per clone at different sites. A trade-off between vegetative growth and reproduction is suggested as a possible cause.