Biodiversity of eukaryotes in large tropical trees: the Life On Trees (LOT) program

Introduction: Basic data on biodiversity, such as the variety of life forms coexisting on a single tree, are still lacking and prevent a full understanding of the complexity of interactions among organisms in a tropical rainforest. Filling this gap has recently become more achievable thanks to advances in canopy access methods and genetic tools. Objective: The main aims of the research program Life On Trees (LOT) are to generate baseline knowledge about the number of species a single tropical tree can support and to understand how these communities of organisms are assembled. Methods: Our first project is performed in one of the most biologically diverse regions: the Peruvian Amazon, in the Rio Abiseo National Park. We focus our sampling on a spectacular Dussia tree (Fabaceae), which is 50 m high and 45 m wide and covered with epiphytes. For safety reasons, the sampling is carried out by professional climbers, guided by experts of the different eukaryotic groups studied (plants, fungi, animals, protists). In order to better understand the contribution of different tree components (bark, leaves, fruits, flowers, dead wood) to overall tree biodiversity, we assign observations into communities based on height zone or microhabitat and examine similarities and nestedness in the composition of these communities. The complex architecture of the tree is studied using terrestrial LiDAR and the location of samples is recorded using a high precision differential GPS receiver (dGNSS). The collected specimens will be determined by classical taxonomy and genetic methods (DNA metabarcoding). An online tracking system for those specimens sent to taxonomists for identification, as well as a central database system, are already under development. Results: The first results of the LOT-Peru project from April-May 2022 and of the preliminary tests conducted in October 2021 will be presented. Implications: The scope of this program is not only scientific. Using the simple example of a large tree, we can reach out to the public and explain difficult concepts, such as what biodiversity is and how it is generated and sustained. In addition, the tree is a strong symbol that has an emotional impact. We hope that this program will build awareness about the impacts of deforestation, and conversely the value of conservation, by showing foresters, city dwellers or villagers that when a tree is cut down, a whole range of biodiversity disappears.