Rapid adaptive evolution to drought in a subset of plant traits in a large-scale climate change experiment

Rapid evolution of traits and of plasticity may enable adaptation to
climate change, yet solid experimental evidence under natural conditions
is scarce. Here, we imposed rainfall manipulations (+30%, control, -30%)
for ten years on entire natural plant communities in two Eastern
Mediterranean sites. Additional sites along a natural rainfall gradient
and selection analyses in a greenhouse assessed whether potential
responses were adaptive. In both sites, our annual target species
Biscutella didyma consistently evolved earlier phenology and higher
reproductive allocation under drought. Multiple arguments suggest that
this response was adaptive: it aligned with theory, corresponding trait
shifts along the natural rainfall gradient, and selection analyses under
differential watering in the greenhouse. However, another seven candidate
traits did not evolve, and there was little support for evolution of
plasticity. Our results provide compelling evidence for rapid adaptive
evolution under climate change. Yet, several non-evolving traits may
indicate potential constraints to full adaptation.