Within and Between Plant Variation in Seed Number, Seed Mass and Germinability of Primula elatior: Effect of Population Size

Abstract: In this study, natural variation of seed mass and seed number between and within individual plants of P. elatior, a common forest herb on rich soils in Flanders, was investigated for both small (< 50 flowering individuals) and large (> 1000 flowering individuals) populations. The relationship between seed number and seed mass at both the between and within population level was also quantified. We also investigated how population size affected germinability of seeds through the effects of seed mass. Seed number varied by a factor of twenty, whereas seed mass spanned, on average, a 3.5 range. In both cases variation was highest among populations, indicating that population size has important effects on seed number and seed mass. Next, seed number-seed mass tradeoffs were significantly influenced by population size, with small populations showing strong negative relationships whereas in large populations seed mass was only marginally influenced by seed number. As to germination, larger seeds showed larger germination percentages only for the smallest population. In all other populations, seed mass had little effect on germination.