Evolution in a rare plant in response to drought

As climate change continues and the frequency and intensity of droughts
become more prevalent in some regions, plant populations are facing
greater ecological pressures. The objective of this study was to observe
the response of a rare plant species to an extreme drought event
associated with climate change. To study this response, we collected seeds
from three populations of Collinsia multicolor (San Francisco collinsia,
Plantaginaceae) found in central California both before and after the
state's historic 2012- 2016 drought. We used a greenhouse study to
examine contemporary evolution between the collection years, and included
a drought treatment to study plasticity. We measured three traits that
indicate life history, morphological, and physiological responses to
drought, including flowering time, stomatal density, and chlorophyll
fluorescence. In our two coastal populations, where interannual moisture
variation is greatest, we observed evolution only in stomatal density,
while we observed plasticity in all measured traits. In contrast, our
driest inland population showed no response to the drought or to our
watering treatments, which is consistent with other studies that have
found less response to drought in pre-adapted populations. Overall, our
results suggest that plasticity is favored in variable environments.
However, they also highlight that the pace evolution may be insufficient
to respond to current environmental change.cont