Flowering plants interact with two major suites of insect foragers: pollinators and herbivores. The potential influence of insect foragers on plant resource allocation and consequences for plant fitness is relevant to the study of the evolution of plant traits. Resource allocation theory has particularly neglected the influence of pollinators on fitness consequences of life history patterns in flowering plants, despite the clear influence of pollination on reproduction in flowering plants. We created a model to measure fitness in response to pattern of resource allocation and strength of herbivory and pollination for annual, perennial, and clonal perennial plants. Our dynamic optimization model identifies a dynamic resource pool from which plant resources manifest as leaf biomass, clonal stem biomass, floral biomass and storage biomass. Asexual fitness occurs via clonal reproduction, characterized by high probability of establishment but low dispersal rate, and subject to herbivory. Sexual fitness occurs via pollination of flowers, characterized by low probability of establishment and high dispersal rate. Annual life cycles offer no option for storage, while the perennial life cycles allocate to storage and allows for multiple seasons.
Results/Conclusions
Preliminary model runs indicate that fitness for annual plants is high for a broad range of allocation patterns when herbivory is low and pollination high, but when herbivory is increased and pollination decreased, fitness is highest for allocation patterns that quickly switch from growth to flowering. Changes in pollination appear to have greater effect on fitness than changes in herbivory for annual plants. Fitness is low when pollination occurs early in a growing season, but high when pollination occurs late, regardless of when peak herbivory occurs. Results suggest that for an annual life cycle, strength and timing of pollination are more important than herbivory, although pollination interactions are frequently neglected in allocation models. Adding multi-season dynamics, clonality, and weighting sexual and asexual fitness by establishment and colonization probabilities may clarify subtle effects of herbivory and pollination on different plant life cycles.
