Androsace septentrionalis and the warming meadow: A montane forb's response to long-term experimental warming

Background/Question/Methods

When climatic change surpasses tolerance limits, plant and animal populations have three possible general responses-- they can adapt to their local changing environment, migrate to more suitable habitats, or go extinct.  Our research explores the hypothesis that adaptation and migration play important roles in preventing the extinction of a short-lived montane wildflower in a warming mountain meadow.  In the West Elk Mountains of Colorado, Androsace septentrionalis L. (Primulaceae) spans an elevation gradient of 2,682 m – 4,094 m as well as the microclimate gradient of an experimentally warmed meadow (“the Warming Meadow”) at Rocky Mountain Biological Laboratory (Gothic, CO, elev. 2,920 m).  We use a combination of yearly monitoring, reciprocal transplant experiments, and greenhouse common gardens to characterize A. septentrionalis’ response to both natural and experimental climate variation.

Results/Conclusions

Twenty-one years of experimental warming have caused a 4-fold decline in the abundance of A. septentrionalis reproductive individuals (Control Plots= 206.60 +/- 39.77; Warmed Plots= 45.00 +/- 44.46; p=0.030) and a ten-fold decline in the numbers of seedlings. Despite this decline, the proportion of established individuals that are reproductive is greater in warmed plots than control plots (Control Plots= 0.12 +/- 0.02; Warmed Plots= 0.20 +/- 0.03; p=0.058).   Experimental warming has also caused a significant shift in A. septentrionalis phenotypes toward those common at low-elevations; warmed-plot individuals have larger rosettes, longer stalks, produce more flowers, and flower earlier than control-plot individuals.   When field-collected seeds from the Warming Meadow and along A. septentrionalis’ elevation gradient are grown in common gardens, phenotypic differences in flowering time, stalk-length, and leaf-width are maintained.  Maintenance of these directional life-history and phenotypic shifts in common garden environments suggest A. septentrionalis may be adapting in situ to experimentally warmed microsites.