ECOLOGICAL GENETIC-VARIATION IN SEED BANKS .3. PHENOTYPIC AND GENETIC-DIFFERENCES BETWEEN YOUNG AND OLD SEED POPULATIONS OF CAREX-BIGELOWII

(1) Three approaches were used to determine if phenotypic and genetic variation existed among seed subpopulations of different ages within an Arctic seed bank: (i) morphology and growth rate of seedlings were compared under a common environment; (ii) morphology, growth rates and ecological response to temperature-controlled environments and density were compared using vegetative offspring (ramets); (iii) relative competitive responses of ramets were compared under multiple environments. (2) Phenotypic differences in leaf length and number of leaves were demonstrated among the subpopulations. Seedlings of the young subpopulation initially had longer leaves, but this difference was lost within 4 weeks indicating that the difference was probably of maternal or historical origin. The young subpopulation consistently maintained a greater number of leaves across environments and through time, however. These differences indicate that genetic change occurred in the population under natural conditions within c. 200 years. (3) Consistent differences in response to environment and density were also found. The old subpopulation did not show as great a response to increasing temperature as the young subpopulation. Also, biomass of the old subpopulation was unaffected by an increase in density, whereas the young subpopulation showed less growth at increased density. The origin of these differences are probably due to evolutionary change within the extant, seed-producing population rather than genetic change occurring within the seed bank. Differential response to density was not reflected in a difference in relative competitive ability.