ECOLOGICAL GENETIC-VARIATION IN SEED BANKS .2. PHENOTYPIC AND GENETIC-DIFFERENCES BETWEEN YOUNG AND OLD SUBPOPULATIONS OF LUZULA-PARVIFLORA

(1) Genetic change over time in a population of Luzula parviflora was investigated by germinating seeds from a seed bank that was time-stratified beneath a solifluction lobe at Eagle Creek, Alaska. The oldest subpopulation was inferred to be approximately 150 years old. (2) Seven censuses were conducted to compare morphological and growth traits between young (recently buried) and old subpopulations as well as between the young subpopulation and the active seed bank. (3) When plants which germinated directly from the seed bank were grown in a common environment, subpopulations differed for nearly all variables measured. Young subpopulation plants were initially smaller than plants from other subpopulations, but because of significantly higher growth rates, many of the differences in size were not significant by the final census. (4) Differences which may have been due to maternal/environmental effects were minimized by clonally replicating all genotypes from young and old buried subpopulations. Each genotype was subjected to three nutrient levels. For morphological traits that differed, the young subpopulation tended to be larger than either the plants from the active seed bank or the old subpopulation. In the same comparisons, growth rates of plants from the young subpopulation tended to be less. In addition, there was a tendency (P < 0.10) for the young subpopulation to respond differently to nutrient treatments. (5) Persistent phenotypic differences in both the common and multiple-environment experiments demonstrate genetic differences between different-aged subpopulations of L. parviflora. These differences may be the result of selection or drift acting over approximately 150 years.