Mia Akbar MSc Student, Colautti Lab Examining phenological trade-offs under biotic and abiotic selection in Lythrum salicaria Studies measuring phenotypic selection on day of first flower or “flowering time” in natural populations commonly observe directional selection for early flowering. Paradoxically, phenological responses to climate change are highly variable and do not demonstrate a unilateral shift to earlier flowering time. The timing of flowering is only one part of the overall “flowering schedule” and may trade-off with other adaptive aspects such as duration and peak flowering time, offering one potential resolution to this apparent contradiction. Furthermore, variation in growing conditions across years may maintain variation in the flowering time phenotype and offer an additional explanation for the lack of evolution in response to selection for earlier flowering. Focusing on the North American invasive plant Lythrum salicaria, I use common garden experiments to investigate whether flowering time correlates with other characteristics of the flowering schedule, how variation in annual growing conditions and insect herbivory have the potential to alter the strength of selection on flowering time and whether these relationships differ by latitude of origin. I discovered that detailed metrics of the flowering schedule vary along a latitudinal gradient and that responses to insect herbivory were highly variable across years of the experiment, demonstrating two potential mechanisms that contribute to the “paradox of evolutionary stasis” in the flowering time trait.
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