DEMOGRAPHY OF AN AGE-STRUCTURED ANNUAL - RESAMPLED PROJECTION MATRICES, ELASTICITY ANALYSES, AND SEED BANK EFFECTS

The role of age-structured seed banks in influencing population dynamic parameters was investigated in a natural population of the winter annual Collinsia verna. Seed persistence was quantified by creating experimental seed banks in the field with seeds of known age. Survival and fecundities of adult plant stages were determined in quadrats of naturally occurring individuals in the field population. Bootstrapping was applied to the resulting data set to estimate means and 95% confidence intervals for population growth rate, stable age distributions, reproductive values, and elasticities. Analyses were performed to determine the extent of variation in these demographic parameters between two consecutive years and between three transects within each year. The results indicate that the presence of a seed bank, even of short duration, was critical to the demography of this population. The population was expanding rapidly in the 1st yr of the study (growth rate 1.80), but was declining during the 2nd yr (0.4 1). While the seed bank was demographically important in some transects during the good year (Year 1), the demographic effects of the seed bank were seen most significantly in the poor year (Year 2). The results of this study indicate the need for including age-structured seed banks in demographic analyses and the potential importance of seeds in age-structured seed banks in the shaping of plant life histories.