LIFE-HISTORY DIFFERENCES BETWEEN CENTRAL AND MARGINAL POPULATIONS OF THE CLONAL AQUATIC PLANT RANUNCULUS-LINGUA - A RECIPROCAL TRANSPLANT EXPERIMENT

Different life-history traits of marginal and central populations of the pseudoannual aquatic plant Ranunculus lingua were compared in a reciprocal transplant experiment. Ramets from marginal and central populations performed relatively equal at the marginal habitat, whereas marginal ramets suffered a greater reduction in most growth measures at the central habitat. Insect herbivory and fungal infections had a great impact on ramets at the central site, but was insignificant at the marginal site. The allocation pattern to rhizomes differed between ramets from the two populations in two traits; viz. the number of rhizomes produced per mother ramet and the average rhizome size. Irrespective of transplant site, marginal ramets produced more but smaller rhizomes, whereas central ramets produced individually larger but fewer rhizomes. This trade-off pattern was related to differences between the habitats. The importance of producing large rhizomes in the central habitat was strongly supported by the fact that initially small ramets were more likely to be diseased and more damaged by grazing than initially larger ramets. In the marginal habitats, on the other hand, where mainly density-independent mortality from abiotic factors seems to control ramet populations, a life-history that emphasises producing many, rather than large, vegetative offspring would be favoured.