Climate effects on flowering cues of ornithophilous plants in a Costa Rican cloud forest

Abstract The influence of a changing climate on the phenology of organisms in a region is dependent on how regional climate cues the timing of local life history events and how those cues are changing over time. There is extensive evidence of phenological shifts in flowering time over the past 50 years in response to increasing temperatures in temperate regions, but far less is known about tropical regions where seasonality is less temperature driven. We examined historical datasets of flowering patterns in two guilds of ornithophilous plants in the montane cloud forests of Monteverde, Costa Rica in order to test the hypothesis that drought accumulation patterns rather than temperature cue flowering. Bimonthly censuses of flower production were used to quantify flower production during two sampling periods:1981–1983, 1986–1991, the species studied here appear to cue flowering patterns to either accumulated drought units or a combination of accumulated drought units and chill units prior to flowering. These results have implications for how tropical cloud forest plants will respond to climate change to the extent that drought and chill patterns are changing with time.