Convergent evolution in angiosperms adapted to cold climates

Convergent and parallel evolution occur more frequently than previously thought. Here, we focus on the evolutionary adaptations of angiosperms at sub-zero temperatures. We begin by introducing the history of research on convergent and parallel evolution, defining all independent similarities as convergent evolution. Our analysis reveals that frost zones (periodic or constant), which cover 49.1% of Earth's land surface, host 137 angiosperm families, with over 90% of their species thriving in these regions. In this context, we revisit the global biogeography and evolutionary trajectories of plant traits, such as herbaceous form and deciduous leaves, that are thought to be evasion strategies for frost adaptation. At the physiological and molecular levels, many angiosperms have independently evolved cold acclimation mechanisms through multiple pathways in addition to the well-characterized C-repeat binding factor/dehydration-responsive element binding protein 1 (CBF/DREB1) regulatory pathway. These convergent adaptations have occurred across various molecular levels, including amino acid substitutions and changes in gene duplication and expression within the same or similar functional pathways; however, identical amino acid changes are rare. Our results also highlight the prevalence of polyploidy in frost zones and the occurrence of paleopolyploidization events during global cooling. These patterns suggest repeated evolution in cold climates. Finally, we discuss plant domestication and predict climate zone shifts due to global warming and their effects on plant migration and in situ adaptation. Overall, the integration of ecological and molecular perspectives is essential for understanding and forecasting plant responses to climate change.