Phenology of tropical tree species – environmental cues, molecular mechanisms, and consequences for plant-animal interactions

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Phenology including flowering, fruiting, bud burst, and leaf senescence is vital for the fitness of trees in their local habitats. Temperate tree species use cues such as temperature or day length to time these phenological transitions. For temperate regions, there is already a good base of knowledge on the environmental cues, the molecular basis and the consequence of phenological transitions for structuring plant-animal interactions, while, in contrast, such knowledge for tropical trees is still scarce. Many tropical tree populations exhibit regular and synchronized phenological transitions but there is uncertainty about the environmental cues used by them to regulate phenological transitions. Furthermore, we know virtually nothing about the underlying regulation of genes, or about the effects of phenological transitions on tree physiology and plant-animal interactions in the tropics. Investigating tropical tree phenology thus requires an integrative approach that takes into account the monitoring of tree phenology, molecular methods to study gene expression, and ecological approaches to study plant-animal interactions.This study will be carried out in the montane humid forests and the seasonally dry tropical forest of Southern Ecuador, at the research stations Estacíon Científica San Francísco and Estacíon Científica Laipuna. Here, available data from previous and ongoing projects and a continuous measurement of important parameters such as climate and carbon flux provide an ideal basis for realizing a study on tree phenology. During this project we will simultaneously monitor phenological transitions, changes of gene expression, stem diameter variation, optical properties of canopies in four tree species and link this to carbon fluxes and climatic parameters. Thereby, this project will provide insights on how phenological transitions are triggered, which gene regulatory networks are involved in phenological transitions, and how these influence plant growth and carbon sequestration. Further, I will study the interdependencies of trees and their mutualistic and antagonistic partners in the light of phenological transitions. First, I will investigate pollinator assemblages, pollen-mediated gene flow, seed set, and germination rates. Second, I will investigate associated herbivore assemblages and rates of herbivory over time. Overall, this project will make important contributions to future predictions of the impact of climate change on montane rainforests.