Keeping up with the heat: long-term dynamics and plasticity of heat tolerance in a tropical plant community.

Increases in global temperatures pose immense challenges for plants, especially for tropical species adapted to thermally stable conditions. We therefore investigated the long-term dynamics of photosynthetic heat tolerance in a tropical Zingiberales community of 35 species in a tropical wet forest in the Caribbean lowlands of Costa Rica, using censuses spanning 7 yr. We asked: (1) Does heat tolerance of the Zingiberales community vary across years? And if it does, is this interannual variation associated with changes in environmental temperatures? (2) Do species differ in their interannual plasticity, and does this difference alter their relative heat tolerance rankings over the years? We found significant variation in heat tolerance among years, and while the ranking among species was maintained across years, we found no relationship between heat tolerance and temperature. We also found a trade-off between constitutive heat tolerance and observed plasticity, where species with higher baseline heat tolerance exhibited a reduced capacity for acclimation. This study highlights the importance of long-term monitoring, while the consistent species rankings and the heat tolerance-plasticity trade-off suggest that vulnerability to warming may be predictable, allowing conservation efforts to target specific lineages.