Probability of clonal identity: Inferring the relative success of sexual versus clonal reproduction from spatial genetic patterns

1. For terrestrial plants capable of both vegetative propagation and sexual seed production, we can distinguish clones from the spatial genetic pattern of plants using multi-locus measurement of allozymes, or other molecular markers. 2. The probability of clonal identity F(r) is defined as the probability that a randomly chosen pair of plants separated by a distance r belong to the same clone. It can be estimated from spatial genetic patterns of plants determined by multi-locus molecular methods. 3. If genotypes have the same competitive ability (no local adaptation), diffusion approximation shows that the equilibrium clonal identity function F(r) is proportional to exp [- cr]/√r. 4. The exponential rate of decline with distance, c, equals √(2u/vσ²), and is determined by the relative success of sexual vs. vegetative reproduction (u/v) and the mean square parent-offspring distance in successful vegetative propagation (σ²). 5. We carried out computer simulations to confirm the usefulness of this formula in inferring demographic processes from spatial genetic data. The results hold irrespective of the dispersal range of sexual seeds. The integral of the probability of clonal identity is closely related to the average clone size.