Organisms must be able to adapt in order to persist in dynamic and unstable environments. Now, in the face of rapid environmental change, questions about plants' intrinsic tolerance to variability and unpredictable environments are especially relevant. The timing of both winter freeze-up and spring thaws are unpredictable and under these variable environments, clonal populations of Spirodela polyrhiza (greater duckweed) provide an excellent case study of phenotypic diversification as a risk aversion strategy. Previous research on this species has demonstrated that potential diversification bet hedging in the phenology of the production of turions-the quiescent overwintering structure that rests at the sediment surface-is generated by birth order within clones. Like production of turions which occurs in the fall, the timing of turion reactivation the following spring may also have profound fitness consequences due to the risk of the thaw and re-freezing of the water's surface. I therefore hypothesize that variance in turion reactivation phenology within clones is influenced by birth order of turions. This was tested through a laboratory study that determined the source of observed phenological variability, and an outdoor mesocosm study that further examined fitness consequences of variance in the timing of turion reactivation under different temperature treatments. The results showed that both temperature and birth order play a role in reactivation timing in that early birth order turions generally reactivate before later birth orders. The effect size of this birth order interaction was found to decrease with temperature. Furthermore, although an effect of turion birth order on lineage performance was not seen, temperature was shown to be positively associated with performance. This research suggests mechanisms whereby clones may generate diversification strategies. If various phenotypes (birth orders) perform differently depending on the environment, a "phenotype-by-environment interaction" generates potential diversification bet hedging. Such diversification could mitigate impacts of both seasonal unpredictability and larger scale climate trends. This thesis could not have been done without the help and support of a number of individuals. I would first like to thank my thesis supervisor Dr. Andrew Simons, who has been a wonderful research supervisor and mentor and has endlessly supported me throughout my studies in his lab. His expertise in research and writing have been a great example for me as I navigated my way through my degree program.

Organismal persistence attests to adaptive responses to environmental variation. Diversification bet hedging, in which risk is reduced at the cost of expected fitness, is increasingly recognized as an adaptive response, yet mechanisms by which a single genotype generates diversification remain obscure. The clonal greater duckweed, Spirodela polyrhiza (L.), facultatively expresses a seed-like but vegetative form, the ‘turion’, that allows survival through otherwise lethal conditions. Turion reactivation phenology is a key fitness component, yet little is known about turion reactivation phenology in the field, or sources of variation. Here, using floating traps deployed in the field, we found a remarkable extent of variation in natural reactivation phenology that could not be explained solely by spring cues, occurring over a period of ≥ 200 days. In controlled laboratory conditions, we found support for the hypothesis that turion phenology is influenced jointly by phenotypic plasticity to temperature and diversification within clones. Turion ‘birth order’ consistently accounted for a difference in reactivation time of 46 days at temperatures between 10 and 18 °C, with turions early in birth order reactivating more rapidly than turions late in birth order. These results should motivate future work to evaluate the variance in turion phenology formally as a bet-hedging trait.