S1-11 Friday, Jan. 4 14:30 - 15:00 Temporal Variation as a Driver of Species’ Distribution Patterns EMERY, NC*; LA ROSA, RJ; University of Colorado Boulder; University of Colorado Boulder Nancy.Emery@Colorado.edu https://www.colorado.edu/lab/emery/
Organisms exhibit diverse strategies for managing changes in their environment: some avoid it by specializing on subset of conditions, others rely on adaptive phenotypic plasticity, and still others maintain a conservative bet-hedging strategy that minimizes variance in fitness over time. Understanding how these different strategies arise, and the circumstances that favor one strategy over another, may be critical to explaining plant distribution patterns and how they will respond to future environmental change. Here, we tested if variation in plant strategies for managing temporal heterogeneity can explain the fine-scale distribution patterns of three co-occurring annual congeners across flood gradients in vernal pool wetlands of California. We quantified variation in traits and fitness for each species under four different hydroperiods and three different levels of variability in a stochastically-fluctuating water table. We found that growing at or below the water table reduced the performance of all species – even those that regularly occupy flooded positions in vernal pools. Furthermore, the species that occupy more hydrologically stable microhabitats were less tolerant of stochasticity in the flooding regime. Finally, the fitness benefits of phenotypic plasticity changed with the degree of stochasticity in the water table, emphasizing that phenotypic plasticity is not advantageous when environmental change is not predictable. These results emphasize that species’ adaptations for managing temporal variation can be an important and under-appreciated driver of distribution patterns.