DIFFERENTIAL PHENOLOGICAL SHIFTS IN EUTERPE EDULIS MART. DURING AN EXTREMELY DRY YEAR ALONG AN ALTITUDINAL GRADIENT

Abstract

Temporal variation in rainfall and temperature, which is likely to increase in frequency due to climate change, may cause changes not only in the endogenous rhythms of organisms, but also in their phenology. This is of great concern, because ecological mismatches caused by phenological shifts may affect not only individuals but entire communities, via disruption and cascade effects in diverse ecological processes. Here, we tested the sensitivity of the phenology of Euterpe edulis Mart. to a period of extreme drought, using phenological data for three populations occurring from 0 to 1,200 m a.s.l.. Euterpe edulis is a Neotropical palm that is ecologically important because of its abundance and diverse frugivorous interactions. Three phenophases (flowers, unripe fruit, and ripe fruit) were recorded monthly from June 2014 to May 2017. Additionally, seeds were collected in 2014 and 2015 to assess wet and dry mass variation. The intensity of the drought varied with altitude. The main differences between populations were earlier flowering, a longer fruit maturation period, and larger seeds at higher altitudes. In the year of the severe drought, there were marked decreases in the synchrony of flowering and unripe fruits in the high-altitude populations. All populations exhibited decreases in seed water content, but only the high-altitude populations had decreases in seed dry mass, probably due to the drought. Despite differences in the total annual rainfall, there was relatively similar exposure to the intense drought across the altitudinal range. Populations did however differ in their sensitivity to drought, and the high-altitude populations were not able to maintain synchrony in the flowering and unripe fruit phases. Extreme events in which both climatic and biotic responses were observed were thus related to distinct population thresholds to rainfall shifts in an endangered tropical keystone palm species.