les seminaires de l’ISYEB accueillent Tristan Charles-Dominique de l› Institute of Ecology and Environmental Sciences du CNRS

Contrary to historical views, recent research suggests that the distribution of many tropical biomes is not primarily determined by climate but rather depends on the conditions created by the organisms that compose them. This is particularly obvious in fire-dominated savannas where the main environmental filter (fire) is largely determined by the properties of the grass layer. This talk will synthesise works from Hluhluwe-iMfolozi (South Africa) to quantify the relative effects of three biotic drivers on tree communities: fire, browsing and shading. We will present and discuss the ecological thresholds at which the functional strategies of trees shift (based on their response traits, i.e. traits that allow trees to face an environmental constraint), revealing abrupt changes in ecosystem functioning. In a second part, we will then question how trees can engineer their environment (using effect traits, i.e. traits that modify their direct environment) and discuss hypotheses related to the reinforcing mechanisms responsible for ecological stability. In a second part, I will show how this ecological information can be summarized using a trait approach and can be used to draw hypotheses about macroevolution at larger scale. I will illustrate this point by showing how the use of dated phylogenies helped understanding the emergence of African savannas and introduce some recent development about the emergence of Asian open systems.