Influences of Environmental Variability, Genetics and Plant Size on Variation in Sexual and Clonal Reproduction and Allocation of Resources in Three Wetland Plant Species

Optimal Partitioning Theory (OPT) states organisms will give more resources to structures and functions that enhance fitness. OPT can be applied to reproduction in clonal plants, which allocate resources between two modes of reproduction--sexual through fruits and clonal through spacers and ramets. In nutrient rich environments, clonal growth allows offspring to stay in beneficial surroundings, while in nutrient poor conditions, sexual reproduction can allow escape and generation of new, potentially more fit offspring. I tested this hypothesis by comparing clonal and sexual reproductive allocation in Penthorum sedoides under differing nutrient levels over two generations. Genotypic and environmental influences on reproductive variation in Lythrum salicaria and Penthorum sedoides were separated by comparing clones within and between treatments. Allocation to fruits was higher in the control than the fertilized group, but only in the second year, providing partial support to an increase in sexual allocation in lower resource conditions. Allocation to spacer mass and ramet mass increased under high nutrients, while number of ramets did not, also providing limited support to the predictions of OPT. Genotype had little effect on sexual and clonal variation. Variation due to fertilizer was more influential, demonstrating plasticity in reproductive expression. The two species differed in their reaction to nutrient levels, potentially a consequence of their differing clonal strategies. Optimal Partitioning Theory also predicts that in situations detrimental to survival, such as herbivore attack, plants will invest less in sexual reproduction and more in clonal growth to aid tissue replacement and survival. I compared reproductive responses of three wetland species--Eupatorium perfoliatum, L. salicaria and P. sedoides--inflicted with simulated herbivory--leaf damage, root damage, both root and leaf damage and undamaged controls. Sexual reproduction in P. sedoides was reduced after root damage while it increased with roo