Climate of origin constrains phenological tracking of temperature in a California endemic oak (Quercus lobata)

The study examines the impact of climate of origin and annual temperatures on phenology, or the timing of leaf elongation, in Quercus lobata, a California endemic oak species. Researchers analyzed a nine-year dataset of 659 families of Quercus lobata that were grown in two common gardens. The study found that year-to-year environmental variation had a greater effect on phenological variation than genetic differences linked to the climate where the trees originated.

However, trees from cooler climates were found to have less capacity to adjust their leaf emergence timing to match spring temperatures compared to trees from warmer climates. The research also suggests that strong selection for earlier phenology is unlikely, and there is no evidence that natural selection has favored increased plasticity in Quercus lobata.

This indicates that phenological plasticity, although a crucial factor in how plants respond to changing temperatures, is constrained by natural selection. As temperatures continue to rise, this constraint may disproportionately limit the ability of trees adapted to cooler climates to modify their phenology in alignment with spring temperatures.