An ecological basis for the conservation of Polygonatum verticillatum (L.) All., Whorled Solomon's seal, in Scotland
The population dynamics, vegetative propagation, sexual reproduction, ecology and genetic variation of the rare Scottish plant, Polygonatum verticillatum (L.) All., Whorled Solomon's-seal, were examined. Comparisons were made with populations in Scandinavia where the plant is relatively common. Differences between individual populations and between the two geographic areas are discussed in the context of the rarity and conservation of P. verticillatum in Scotland. Where possible, stages of reproductive failure were identified. Flowering incidence is positively correlated with above-ground shoot size which in turn is related to rhizome biomass. Soil data and other ecological information suggest rhizome growth rates reflects soil nutrient status, and the plant is more likely to flower and to resist competition in nutrient status, and the plant is most likely to flower and resist competition in nutrient-rich sites. Low densities of flowering shoots and a lack of insect pollination appear to be the two most important factors limiting fruit-set in the Scottish populations. In one site there is a high incidence of flower bud abortion and pollen invariability. Preliminary analysis of genetic diversity using RAPDs revealed very low clonal diversity in both the Scottish and Scandinavian populations sampled. Seedlings were found in fewer than half of the Scottish and Scandinavian populations, but infrequent seedling recruitment may still be important in maintaining or increasing genetic variation within populations. The response of the plant to management was assessed by trial experiments in two Scottish sits and by observing populations in managed vegetation in Scandinavia. In a heavily shaded site flow production of P. verticillatum increased after more light was made available, and in a site dominated by single-whorled shoots of P. verticillatum, shoot size increased after the addition of sol nutrients. P. verticillatum is associated with ancient wooded meadows in Scandinavia where the traditional use of fire to burn litter may have favoured the plant's survival by suppressing competitors.