Abstract The increasing drought frequency and intensity requires a deeper understanding of adaptive mechanisms in forest trees. This study investigated drought responses in Pinus pseudostrobus sensu lato, by analyzing genetic variation and phenotypic plasticity across 60 progenies from five varieties ( pseudostrobus, oaxacana, apulcensis, coatepecensis , and estevezii ). Growth, survival, and morpho-anatomical traits of seedlings were assessed under two watering regimes in a common garden trial. Drought reduced seedling growth and altered leaf structure with pronounced effects on height and diameter growth, needle length and thickness, stomatal characteristics, and specific leaf area. Response varied both among and within varieties, with estevezii and apulcensis showing better performance under drought, expressing more conservative, xerophytic traits and adaptive plastic responses. Correlations between these traits and seedling performance strengthened under drought conditions, highlighting their adaptive value and suggesting that water deficit enhances expression of functional trait-performance relationships. Importantly, differences in trait expression and performance were linked to the climatic conditions of origin, highlighting the role of environmental niche in shaping genetic differentiation and adaptive strategies. Phenotypic plasticity was most evident in foliage developed during drought and varied by trait and family, suggesting genetic effects. Plasticity tended to be negatively associated with seedling performance under drought, but positively under well-watered conditions, indicating a trade-off between productivity and stress tolerance. These results provide strong support for ecotypic differentiation in P. pseudostrobus and emphasize the importance of incorporating genetic diversity and local adaptation into forest management, breeding, and conservation strategies to address challenges posed by climate change.
Escobar-Alonso et al. (2025) studied this question.