Effects of local density of clonal plants on their sexual and vegetative propagation strategies in a lattice structure model

Clonal plants can propagate both sexually and vegetatively and the balance between the efforts of sexual and vegetative propagation can be determined by inter- and intra-specific competition. This raises the question of whether sexual propagation becomes more suitable than vegetative propagation or vice versa. Some studies suggest seed production is positively correlated with plant density, and others, negatively. To evaluate the effects of local density of ramets on plant propagation strategy, we developed a lattice model where two strategies compete with each other. In the model, a plant changes its strategy based on local density as defined by the proportion of neighboring lattice cells containing plants. One strategy produces seeds at high local density (SEEDING at HLD) and produces ramets at low local density, and the other strategy produces ramets at high local density (RAMETING at HLD) and seeds at low local density. Seeds can spread all cells while ramets can reach only adjacent cells, and if an individual from a seed competes with an individual from a vegetative propagule, the latter always wins. Each plant has different thresholds to change its strategy from sexual to vegetative, or vice versa, along with local density. In the model, a realized density depends on both reproductive rate and mortality; thus, we evaluate the performance of each strategy under different mortalities.