Changes in temperature and precipitation drive shifts in mean flowering timing of tropical plants from 1960 to 2021 across seven locations.

It has been shown that changes in plant flowering times are directly tied to climate change, often being the first and most visible indicators of a broader, ecosystem-wide change. Despite this, tropical latitudes have been markedly understudied. We analyzed 19 tropical species across seven locations from 1960 to 2021. Through a series of Bayesian regression analyses of flowering date on maximum temperature, minimum temperature, and precipitation, we found that flowering dates of tropical plants have changed substantially with changes in climate. Flowering dates have shifted an average of 6.9 days per °C of maximum temperature change, 4.5 days per °C of minimum temperature change, and 0.28 days per mm precipitation. We then computed combined effects of the aforementioned climate variables and found that flowering dates have shifted 15.0 days per unit of combined temperature and precipitation changes (computed as the sum of products of standardized changes in climate variables and their posterior effect estimates). We found no meaningful difference in magnitude of change in flowering of species in consistently hot and wet locations to those in locations with seasonal wet and dry periods (Wilcoxon rank sum, P>0.05). Our study demonstrates that tropical ecosystems are not insulated from the impacts of climate change.