MODELING INVESTMENTS IN SEEDS, CLONAL OFFSPRING, AND TRANSLOCATION IN A CLONAL PLANT

Clonal plants that can switch facultatively between sexual and asexual reproduction may respond plastically to the environment. We constructed a dynamic state variable model to examine how the measure of fitness, ramet and genet mortality, and the assimilation rates of a parent and its clonal offspring influence behavioral investments in ramet growth, clonal offspring, seeds, and continued resource translocation to clonal offspring after establishment. The model leads to predictions that ramet and genet mortality rates and/or the fitness payoff from producing seeds must be high for seed production to capture a proportion of reproductive investments. If seed production occurs as a result of high ramet or genet mortality rates, then results indicate that it is better to produce seeds early in the season, regardless of ramet size. In contrast, if seed production is favored as a result of its large contribution to fitness, then it is predicted to depend on ramet size more than on time. While the total amount of biomass directed to reproduction is predicted to increase with a ramet’s own productivity, the proportion of this biomass invested clonally or sexually depends on the resource environment encountered by that ramet’s clonal offspring; more productive surroundings favor investment in clonal offspring that forage locally, reduce the risk of genet mortality, and increase the expectation for future seed production by the genet. The model we present also suggests that a higher rate of translocation to support clonal offspring benefits a genet when the parent and offspring ramets have contrasting productivities. In addition, the model also leads to the predictions that translocation is more advantageous when the currency of fitness selects for increases in ramet size more than ramet number and when the probability of mortality is correlated among ramets.