Density, dispersion and population genetics of a Silene latifolia seed bank from southwestern Virginia

PERONI, P A. AND R. T ARMSTRONG (Department of Biology, Davidson College, Davidson, NC 28035-7118). Density, dispersion, and population genetics of a Silene latifolia seed bank front southwestern Virginia. J. Torrey Bot. Soc. 128:400-406. 2001.-White campion (Silene latifolia) is a dioecious perennial that is the focus of an on-going meta population study in southwestern Virginia. In order to determine if a population in this study region maintained a dormant seed bank we collected soil cores, placed them in a greenhouse, and monitored emergence of white campion seedlings. The timing of soil core collection ensured that all white campion seeds in the soil were greater than or equal to10 mo old. We compared the genetic composition of the seed bank with that of the above ground plants and the seed crop produced that year by scoring individuals from each cohort for sex and genotype at 7 polymorphic isozyme loci. A total of 99 white campion seedlings emerged froth the 70 cores collected (mean density of seedlings per core = 1.41 +/- 4.37, n = 70 cores; 535.29 seedlings/m(2)). The frequency distribution for seedling density per core deviated significantly from that predicted by a Poisson distribution, and the results of this analysis indicate a clumped dispersion pattern. The observed genotype frequencies in each cohort did not differ significantly from Hardy-Weinberg predictions, and allele frequencies did not differ significantly between the above and below ground cohorts. Sex ratios in each cohort did not deviate significantly from 1:1. The results indicate that this white campion population maintains a dormant seed hank that provides an unbiased reservoir of genetic variation for the characters we investigated.