The timing of flowering depends on an environmental trigger or proximal cue and might be modified by additional environmental factors. The environmental triggers and modifying factors that determine flowering times in tropical forests are the subject of conjecture. Hypotheses advance variation in temperature, moisture availability, day length, maximum solar irradiance, and daily solar insolation at the forest canopy or at the top of the atmosphere. We advance the new hypothesis that atmospheric vapor pressure deficits influence flowering times. We evaluate all of these hypotheses in a model selection framework against long-term flower records from tropical forests located at 0⁰41’S (Yasuni), 2⁰58’N (Pasoh), 9⁰08’N (BCI) and 18⁰21’N (Luquillo). Our flower records begin in 2001, 2002, 1987 and 1992, respectively, and include species-level identification of all flowers collected in weekly (Pasoh and BCI) or twice monthly (Yasuni and Luquillo) censuses of 200, 336, 200 and 120 0.5-m2 traps, respectively. Our meteorological data include hourly temperature, rainfall, relative humidity and solar irradiance for Pasoh, BCI and Luquillo.
Preliminary analyses indicate that drought, low temperature and insolation at the forest canopy all influence tropical flowering times. We will complete our analyses before April. We will edit this abstract to include detailed results that are not yet available in April.