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Dryad

Data and code for: Adaptive evolution of freezing tolerance in oaks is key to their dominance in North America

Abstract

Freezing tolerance plays a pivotal role in shaping the distribution and diversification of organisms across diverse habitats and was likely crucial to the expansion and adaptive radiation of the American oaks. We investigated the dynamics of adaptation to climate and potential trade-offs between stem freezing tolerance and growth rate in 48 Quercus species from five genus sections grown under temperate and tropical conditions. Species from colder regions exhibit higher freezing tolerance, lower growth rates and higher acclimation potential compared to species from warmer climates, suggesting evolutionary adaptations to seasonal climate fluctuations. Deciduous species show marked variability in freezing tolerance across their broad climatic range while evergreen species, confined to warm climates, display low freezing tolerance. While annual growth rates are constrained in deciduous species, we found no direct trade-off between freezing tolerance and growth because deciduous species that evolved in warm latitudes lost freezing tolerance. Despite an evolutionary lag, freezing tolerance in Quercus species is closely aligned with its optimal state. The capacity to withstand cold and adapt to a wide range of thermal environments was likely critical to adaptive radiation and current dominance of the North American oaks. Data and code are provided here.