Monkeyflowers Survived California's Worst Drought in 10,000 Years by Evolving Fast Enough

A potted scarlet monkeyflower will die within days without water. In the wild, entire populations of the species should have been wiped out by California's 2012-2016 drought - the most extreme in over 10,000 years. Some were. But others survived, and a new study published in Science explains why: they evolved fast enough to outpace the catastrophe.

The research provides the first complete documentation of evolutionary rescue from climate change in natural populations. Previous work had demonstrated the concept in laboratory settings and in theoretical models. This is the first study of wild populations to document decline due to climate change, evolution of climate adaptations across whole genomes, and subsequent population recovery - the full arc of rescue.

A decade of watching flowers adapt

The study grew from a fortunate accident of timing. Senior author Amy Angert at the University of British Columbia, along with then-PhD student Seema Sheth (now at North Carolina State University), began tracking variations in scarlet monkeyflower populations across Oregon and California in 2010. They were studying natural genetic variation. They did not anticipate that two years later, the most extreme drought in recorded geological history would begin in California.

As populations crashed, the researchers realized they had something rare: a genetic baseline. Seeds collected before the drought, stored back in the lab, served as a time capsule. First author Daniel Anstett, now an assistant professor of plant biology at Cornell University, and the research team used whole-genome sequencing across 55 populations to establish the pre-drought genetic landscape, paying particular attention to genetic variation associated with climate differences across the populations' range.

As the drought progressed, the team tracked how this climate-associated variation changed as populations declined and adapted. Some populations evolved traits that helped them survive. Others declined or went extinct entirely.

The fastest evolvers recovered

Three populations fared particularly well - those with the most genetic variation at climate-associated sites before the drought began. These populations evolved the fastest during the drought and subsequently recovered.

The genetic adaptations appear to be correlated with variations in leaf stomata - the microscopic pores that control gas exchange and water loss - including how much they open or close and how the plant assimilates carbon through photosynthesis. But the exact genes controlling these traits have not been identified. That remains an active area of research.

Perhaps the most striking finding is predictive. The genetic variation present before the drought - measured in 2010, two years before the crisis began - predicted which populations would recover five, six, and seven years later. As Anstett puts it, that pre-existing variation acts as a kind of crystal ball for forecasting a species' ability to survive future climate events.

Successes and failures side by side

Not all populations were rescued. Some lacked sufficient genetic variation at the right sites and could not evolve fast enough. The study documents both outcomes, making it as much a story about why some populations fail as why others succeed.

Evolution, Anstett notes, has no foresight. It is a process, like gravity. The populations that survived were not smarter or luckier in any meaningful sense - they simply happened to carry genetic variants that were useful under drought conditions, and natural selection amplified those variants quickly enough to prevent extinction.

Useful for conservation, but with caveats

The approach could help conservation biologists forecast which species and populations are most at risk from climate change. If pre-existing genetic variation can predict recovery potential, then genomic surveys of endangered species might reveal which populations are most resilient and which need the most intervention.

But the limitations are real. This is one species - a small wildflower - in one region, responding to one type of climate event. Whether the same principles apply to trees, animals, marine organisms, or species with longer generation times and less genetic diversity is unknown. Plants with short generation times can evolve over a few reproductive cycles. A species that reproduces every five years has far fewer chances to adapt before a prolonged drought eliminates it.

The study also does not yet resolve whether the genetic adaptations that helped during the drought will prove beneficial in the long term. Traits that promote survival under extreme drought conditions might be disadvantageous when conditions return to normal. Anstett's lab is currently using seeds from 2017 to 2025 to study what happened to the recovered populations after the drought ended and how their recent evolution positions them for future climate events.

There is also a scale mismatch between what the study shows and what conservation practice needs. Genomic surveys of wild populations are expensive and time-consuming. Translating population-genetics data into practical conservation decisions requires integration with ecological knowledge, land management, and policy - a complicated calculus, as Anstett acknowledges.

Still, the core finding matters: evolution can work fast enough to rescue populations from climate extremes, and the capacity for that rescue can be detected in advance. For a field that often focuses on what we are losing, this is a rare piece of evidence about what some species can do to save themselves.