Alpine Plant Evolution Under Climate and Seasonal Change

Foundational work

The research program at RMBL on alpine plant evolution was anchored by long-term observations of flowering phenology paired with field-based quantitative genetics. A landmark study combined a 38-year flowering record with common garden experiments to show that Boechera stricta has advanced its flowering by roughly a third of a day per year since the 1970s, driven by earlier snowmelt and warmer temperatures, and that this shift reflects both plasticity and genetic adaptation (Anderson et al., 2012). A companion synthesis emphasized that populations facing climate change will rarely persist through a single mechanism, but rather through some combination of migration, plasticity, and adaptation depending on generation time, mating system, and genetic architecture (Anderson et al., 2012). Together with a broader review of plant adaptation genetics (Anderson et al., 2011), these papers established flowering time as a model trait for studying rapid evolution in the wild.

Early QTL work mapped the genetic basis of these traits to specific chromosomal regions. A large-effect locus influencing flowering time was identified and shown to carry a measurable fitness advantage in the field (Anderson et al., 2011), and subsequent genome-wide analyses revealed that local adaptation in B. stricta arises from many loci, with about 8% of the genome showing conditional neutrality and a smaller fraction showing genetic trade-offs between environments (pub from 2013).

Key findings

Across dozens of studies, a coherent picture has emerged: B. stricta populations are locally adapted across elevation, and climate change is disrupting that match. Reciprocal transplants spanning more than 106,000 individuals showed that experimental snow removal — simulating future conditions — cut the probability of reproduction in low-elevation families by 75%, with population growth rates falling below replacement at the lowest gardens (Anderson & Wadgymar, 2020). Snow addition, by contrast, restored local adaptation and shifted the optimum toward lower-elevation genotypes (study from 2017). Snow removal alone advanced flowering by about a week, comparable to two or three decades of warming (study from 2015), and these effects extend across generations: parental snow environments influenced offspring germination and seed mass, with transgenerational plasticity sometimes exceeding within-generation responses (Wadgymar et al., 2018).

Selection on traits is neither simple nor constant. Stabilizing selection on leaf traits emerges only when data are integrated across multiple years, while single-year analyses suggest weaker directional patterns, and viability selection before flowering can oppose fecundity selection afterward (Wadgymar et al., 2017). Herbivory and water availability act as divergent agents of selection on leaf traits, with stabilizing selection on specific leaf area but directional selection favoring greater succulence (Jameel et al., 2025). Defense chemistry is shaped by balancing selection: alternative alleles at glucosinolate-biosynthesis genes have opposite fitness effects under drought versus herbivory, and the resulting chemical polymorphism varies from 0 to 100% across hundreds of natural populations (Carley et al., 2021). Flower color shows a parallel story, with purple-flowered plants more common at higher elevations and on south-facing slopes, lower foliar herbivory on pigmented individuals (study from 2018), and clear environmental and genetic components to the polymorphism (study from 2017).

Genetic architecture also matters for the pace of evolution. A young chromosomal inversion that arose since the last glaciation carries multiple linked loci controlling flowering time and defense, and is under positive selection in a hybrid zone (Lee et al., 2017). But genetic variation for key traits like flowering phenology contracts when plants are grown in warmer, drier conditions, suggesting the raw material for adaptation may shrink precisely where it is needed most (Bemmels & Anderson, 2019). Resource stress further reshapes trade-offs: negative genetic covariances between growth and reproduction appear only under severe drought combined with low nutrients (MacTavish & Anderson, 2020).

Current frontier

Early work in the 2010s established that B. stricta is locally adapted and evolving in response to climate. Recent studies since 2020 have shifted toward integrating evolution with demography to forecast persistence. The most ambitious effort modeled eco-evolutionary dynamics across 102,272 transplants from 115 source populations over up to nine years and concluded that neither local adaptation nor natural gene flow will be sufficient to rescue B. stricta from projected climate change, with the lowest-elevation sites already demographically unsustainable (Anderson et al., 2025). A commentary in Science underscored the severity: gene flow in this largely self-pollinating species is too slow, and unassisted upslope migration cannot keep pace (Aitken, 2025). New experimental work has begun manipulating multiple climate drivers simultaneously, showing that elevated CO2 enhances photosynthesis across genotypes but does not offset the fitness costs of warming (Denney et al., 2024), and that combined CO2 and temperature changes impose novel selection on allocation and leaf traits (Denney & Anderson, 2025).

Methodologically, the field is moving toward longer time horizons, demographic models that project lineage growth rates rather than annual fitness, and explicit tests of how stressors interact. Drought-by-herbivory experiments now show that defense polymorphism may persist across a wide range of conditions but is eroded by increasing aridity, suggesting that climate change could homogenize genetic variation that has been stable for millennia (Carley et al., 2025). Researchers are also paying renewed attention to microrefugia — small patches of cooler or wetter microhabitat that might buffer local populations in the short term (Denney et al., 2020).

Open questions

The central unresolved question is whether assisted migration, microrefugia, or yet-undiscovered sources of plasticity can buy time for populations that natural processes alone cannot save. How will defense polymorphisms, flower color variation, and chemical clines that took millennia to assemble respond to a few decades of rapid drying? Can mutualists like pollinators and antagonists like herbivores shift in concert with their host plants, or will phenological mismatches accelerate decline (Morton & Rafferty, 2017)? And as genetic variation for key traits contracts under future climates, what management interventions — seed transfer, habitat connectivity, targeted protection of high-elevation refugia — could help maintain the evolutionary potential of mountain plant communities? The next decade of work at RMBL is poised to tackle these questions by linking long-term demographic monitoring, genomic data, and multi-factor field experiments at scales that match the pace of environmental change.

REFERENCES

Aitken, S. N. (2025). An uphill grind for wild plant populations. Science. →

Anderson, J. T. (2017). Climate change affects Boechera stricta genotypes through local maladaptation. →

Anderson, J. T. (2017). The maintenance of flower colour polymorphism in self-pollinating Boechera stricta. →

Anderson, J. T. et al. (2011). Life history QTLs and natural selection on flowering time in Boechera stricta. →

Anderson, J. T. et al. (2013). Genetic tradeoffs and conditional neutrality contribute to local adaptation. →

Anderson, J. T. et al. (2025). Adaptation and gene flow are insufficient to rescue a montane plant under climate change. Science. →

Anderson, J. T., Inouye, D. W., McKinney, A. M., Colautti, R. I., Mitchell-Olds, T. (2012). Phenotypic plasticity and adaptive evolution contribute to advancing flowering phenology in response to climate change. Proceedings of the Royal Society B. →

Anderson, J. T., Panetta, A. M., Mitchell-Olds, T. (2012). Evolutionary and ecological responses to anthropogenic climate change. Plant Physiology. →

Anderson, J. T., Wadgymar, S. M. (2020). Climate change disrupts local adaptation and favours upslope migration. Ecology Letters. →

Anderson, J. T., Willis, J. H., Mitchell-Olds, T. (2011). Evolutionary genetics of plant adaptation. Trends in Genetics. →

Bemmels, J. B., Anderson, J. T. (2019). Climate change shifts natural selection and the adaptive potential of the perennial forb Boechera stricta in the Rocky Mountains. Evolution. →

Carley, L. N. et al. (2021). Ecological factors influence balancing selection on leaf chemical profiles of a wildflower. Nature Ecology & Evolution. →

Carley, L. N. et al. (2025). Increasing aridity may threaten the maintenance of a plant defence polymorphism. Ecology Letters. →

Denney, D. A. et al. (2020). Small spaces, big impacts: contributions of micro-environmental variation to population persistence under climate change. AOB Plants. →

Denney, D. A., Anderson, J. T. (2025). Increased temperature and CO2 induce plasticity and impose novel selection on plant traits. Integrative and Comparative Biology. →

Denney, D. A., Anderson, J. T., et al. (2024). Elevated CO2 and temperature augment gas exchange and shift the fitness landscape in a montane forb. New Phytologist. →

Jameel, M. I. et al. (2025). Herbivory and water availability interact to shape the adaptive landscape in Boechera stricta. Evolution. →

Lee, C.-R. et al. (2017). Young inversion with multiple linked QTLs under selection in a hybrid zone. Nature Ecology and Evolution. →

MacTavish, R. M., Anderson, J. T. (2020). Resource availability alters fitness trade-offs: implications for evolution in stressful environments. American Journal of Botany. →

Morton, E. M., Rafferty, N. E. (2017). Plant-pollinator interactions under climate change: the use of spatial and temporal transplants. Applications in Plant Sciences. →

Wadgymar, S. M. (2015). Plasticity in functional traits in the context of climate change: Boechera stricta. →

Wadgymar, S. M. (2018). Ecological causes and consequences of flower color polymorphism in a self-pollinating plant. →

Wadgymar, S. M. et al. (2017). Identifying targets and agents of selection. Methods in Ecology and Evolution. →

Wadgymar, S. M., Daskin, J. H., Anderson, J. T. (2017). Integrating viability and fecundity selection to illuminate the adaptive nature of genetic clines. Evolution Letters. →

Wadgymar, S. M., Mactavish, R. M., Anderson, J. T. (2018). Transgenerational and within-generation plasticity in response to climate change. American Naturalist. →