Abstract Understanding how local climate patterns select for thermal and drought tolerance traits is needed to predict differential responses to climate change across complex ecosystems. Here, we used high‐throughput methods to measure traits that confer heat and drought tolerance across a tropical climatic variability gradient and examined how forest type and leaf habit mediate these traits. We estimated thermotolerance thresholds (Tcrit, T50, T95), drought tolerance traits (water potential at turgor loss point 𝝭 TLP and osmotic potential 𝞹 osm ), and morphological traits (wood density and leaf mass per area LMA) for 92 woody plant species across six sites along a tropical dry‐to‐wet gradient in Área de Conservación Guanacaste, Costa Rica. Among evergreen species, T95 weakly declined with elevation, LMA was positively associated with T50 and T95, and greater drought tolerance values were found at lower elevations and with greater wood density. Among deciduous species, no significant associations were found between tolerance traits and elevation or wood density, though LMA was positively associated with T50. T95 was higher on average among seasonal dry and ecotonal forest species compared with wet forest species. Additionally, evergreen species from dry and ecotonal forests exhibited greater drought tolerance than those from wet forests, whereas drought tolerance indices did not differ among deciduous species across forest types. These results point to multiple adaptive pathways for evergreen species and provide evidence that evergreen trees face greater drought‐induced selection pressure. Surprisingly, thermal tolerance traits were largely decoupled with drought tolerance traits, suggesting that coordination among traits that confer tolerance to environmental stressors is not generalizable in tropical forests. Read the free Plain Language Summary for this article on the Journal blog.
Terry et al. (Sat,) studied this question.