Maurice Leponce ^1,2* Yves Basset ³ Ángela Aristizábal-Botero ¹ Noui Baïben ⁴ Jérôme Barbut ⁵ Bart Buyck ⁵ Philip Butterill ⁶ Kim Calders ⁷ Glenda Cárdenas ⁸ Jean-François Carrias ⁹ Damien Catchpole ¹⁰ Barbara D'hont ⁷ Jacques Delabie ¹¹ Jochen Drescher ¹² Damien Ertz ^13,14 André Heughebaert ¹⁵ Valérie Hofstetter ¹⁶ Céline Leroy ^17,18 Frédéric Melki ¹⁹ Johan Michaux ²⁰ Jhon C. Neita-Moreno ²¹ Eddy Poirier ²² Rodolphe Rougerie ⁵ Germinal ROUHAN ⁵ Vincent Rufray ²³ Stefan Scheu ^12,24 Jürgen Schmidl ²⁵ Alain Vanderpoorten ²⁶ Claire Villemant ⁵ Nabil Youdjou ¹ Olivier Pascal ¹⁹

• ¹ Royal Belgian Institute of Natural Sciences, Brussels, Belgium
• ² Université libre de Bruxelles, Brussels, Belgium
• ³ Smithsonian Tropical Research Institute (Panama), Panama City, Panama
• ⁴ Independent researcher, Lyon, France
• ⁵ Muséum National d'Histoire Naturelle, Paris, France
• ⁶ Biology Centre, Academy of Sciences of the Czech Republic (ASCR), Prague, Czechia
• ⁷ Department of Environment, Faculty of Bioscience Engineering, University of Ghent, Ghent, East Flanders, Belgium
• ⁸ Biodiversity Unit, University of Turku, Turku, Finland
• ⁹ UMR6023 Laboratoire Microorganismes Génome Et Environnement (LMGE), Aubière, Auvergne, France
• ¹⁰ Independent researcher, Lima, Peru
• ¹¹ Cocoa Research Center – CEPEC/CEPLAC, Ilhéus, Bahia, Brazil
• ¹² Johann Friedrich Blumenbach Institute of Zoology and Anthropology, University of Göttingen, Goettingen, Lower Saxony, Germany
• ¹³ Botanic Garden Meise, Brussels, Belgium
• ¹⁴ French Community of Belgium, Brussels, Belgium
• ¹⁵ Belgian Biodiversity Platform, Brussels, Brussels, Belgium
• ¹⁶ Independent researcher, Nyon, Switzerland
• ¹⁷ The AMAP laboratory, Montpellier, Languedoc-Roussillon, France
• ¹⁸ Université des Antilles et de la Guyane, Pointe-à-Pitre, France
• ¹⁹ Fonds de Dotation Biotope Pour La Nature, Remire-Montjoly, French Guiana
• ²⁰ Institute of Botany, University of Liege, Liege, Liège, Belgium
• ²¹ Alexander von Humboldt Biological Resources Research Institute, Bogotá, Colombia
• ²² Independent researcher, Cayenne, French Guiana
• ²³ Fondation Biotope, Remire-Montjoly, French Guiana
• ²⁴ Centre of Biodiversity and Sustainable Land Use, Faculty of Agricultural Sciences, University of Göttingen, Göttingen, Lower Saxony, Germany
• ²⁵ University of Erlangen Nuremberg, Erlangen, Germany
• ²⁶ Department of Biology, Ecology and Evolution, Faculty of Sciences, University of Liege, Liege, Liège, Belgium

Large tropical trees are rightly perceived as supporting a plethora of organisms. However, baseline data about the variety of taxa coexisting on single large tropical trees are lacking and prevent a full understanding of both the magnitude of biodiversity and the complexity of interactions among organisms in tropical rainforests. The two main aims of the research program "Life on Trees" (LOT) are (1) to establish baseline knowledge on the number of eukaryote species supported/hosted by the above-ground part of a single tropical tree and (2) to understand how these communities of organisms are assembled and distributed on or inside the tree. To achieve the first goal, we integrated a set of 36 methods for comprehensively sampling eukaryotes (plants, fungi, animals, protists) present on a tropical tree. The resulting LOT protocol was conceived and implemented during projects in the Andean Amazon region and is proposed here as a guideline for future projects of a similar nature. To address the second objective, we evaluated the microclimatic differences between tree zones and tested state-of-the-art terrestrial laser scanning (TLS) and positioning technologies incorporating satellite and fixed base station signals (dGNSS). A marked variation in temperature and relative humidity was detected along a 6-zones Johansson scheme, a tree structure subdivision system commonly used to study the stratification of epiphytic plants. Samples were collected from these six zones, including three along the trunk and three in the canopy. To better understand how different tree components (e.g., bark, leaves, fruits, flowers, dead wood) contribute to overall tree biodiversity, we categorized observations into communities based on Johansson zones and microhabitats. TLS was an essential aid in understanding the complex tree architecture. By contrast, the accuracy of positioning samples in the tree with dGNSS was low. Comprehensively sampling the biota of individual trees offers an alternative to assessing the biodiversity of fewer groups of organisms at the forest scale. Large old tropical trees provide a wealth of microhabitats that encompass a wide range of ecological conditions, thereby capturing a broad spectrum of biodiversity.