Seedling Recruitment and the Maintenance of Clonal Diversity in Plant Populations--A Computer Simulation of Ranunculus Repens

Abstract

1 A computer simulation model is developed to examine the effects of varying levels of seedling recruitment, mortality and rates of clonal growth on genet diversity in populations of the clonal perennial herb, Ranunculus repens. 2 It is shown, following an initial colonization event, that there is a rapid loss of genets from populations in which there is no further seedling recruitment, and that such populations become dominated by a few large clones. Nevertheless coexistence of a high density of genets is possible in the short term in the nonequilibrium situation occurring immediately after a large scale disturbance. 3 The input of only a few seedlings each year into a population of ramets accelerates the loss of founder genets but acts as a powerful mechanism for maintaining genet diversity in populations. Varying the level of density-dependent mortality and the rate of clonal growth also influences genet diversity. 4 Taking the results of all the simulations together it is demonstrated that it is the ratio of seedling to ramet recruits that is crucial in determining the genetic architecture of clonal plant populations both in terms of the number and size hierarchy of genets. Significant variation in the relationship between population structure and the ratio of seedling to ramet recruits was related primarily to low initial population densities and subsequent low seedling inputs. 5 The low ratio of seedling to ramet recruits observed in many plant populations where seedling recruitment occurs within established populations is shown to be sufficient to maintain quite high genet densities relative to the total number of ramets, unless there is strong competition between genets. 6 Inequality in the genet size of clonal plants increases with time and also with a decrease in the ratio of seedling to ramet recruits, except at very low values where there is again a decrease in inequality. The development of genet size hierarchies in clonal plants is compared with that of aclonal plants.