The high abundance and diversity of plants living as epiphytes, on the nutrient-poor surface of other plants, such as e.g. many orchids and other members of the pineapple family (Bromeliaceae), have long fascinated tropical ecologists. Yet, the reasons explaining the success of this lifestyle and the high diversity of epiphyte species, even on a single tree, remain poorly understood. One possible explanation potentially lies in the facilitating role of the plants microbiota, whether that of epiphytic plants or of their living support, in the germination, growth and coexistence of epiphytic plants. The project EPIFUN tackles this question by focusing on the fungi colonizing the roots of vascular epiphytes, including the mutualistic mycorrhizal fungi. More specifically, EPIFUN addresses five main scientific objectives: (i) to determine whether the fine-scale spatial distribution of fungal communities on bark surface co-varies with the presence of epiphytes; (ii) to assess whether root-associated fungi are specific to their epiphytic host or whether they exhibit a “horizontal structure”, i.e. depend on the identity of the supporting trees, or a “vertical structure”, caused by local environmental gradients from the roots to the top of tree crowns; (iii) to experimentally test to which extent fungi constrain the distribution of epiphytes on certain phorophytes, particularly when a specific fungal symbiont is required for germination and growth of the epiphytic plant; (iv) to assess if segregation or sharing of root endophytic fungi drives the coexistence of epiphytic species on trees, and if this pattern is consistent along a gradient of stress for epiphytes; (v) to determine to which extent epiphytes gain carbon by fungal pathway, from neighboring epiphytes and from the supporting tree itself. EPIFUN is intended to promote the development of a new research team in its host institution, i.e., Institut de Systématique Evolution Biodiversité (UMR7205), working on the new promising topic of plant-microbiota interactions in tropical ecosystems, and approaching the supports for epiphytic plants as living communities rather than mere physical supports. For this purpose, the project brings together young and mid-career scientists, including experts on: (i) taxonomy, systematics and ecology of tropical epiphytes, especially orchids, lycophytes and ferns, to carry out field studies in the tropical areas covered by EPIFUN, i.e. La Réunion and French Guiana; (ii) environmental genomics and fungal metabarcoding precisely, to achieve the identification of fungal communities from the roots and from the epiphytic substrata directly; (iii) bioinformatics, biostatistics, and community ecology to analyse the data; (iv) experimental approach (including isotopic labelling) to assess functional aspects of the plant-fungal interactions. As a multidisciplinary project in an overlooked field of research, EPIFUN is expected to have an impact among the scientific audience covering environmental genomics, tropical ecology, fungal ecology, plant ecology and physiology, and plant and fungal systematics. This project is not only committed to research but also to education and dissemination of scientific knowledge. First, it is meant to be attractive for new PhD students and post-doctoral researchers. Last but not least, it is meant to be attractive for the general public by tacking advantage of the attendance levels of its host institution, the Muséum national d’Histoire naturelle (MNHN), and by organizing outreach in the French regions where sampling and experiments will take place.

Beyond their role in artistic creation and symbolic expression of prehistoric societies, colouring materials were involved in different kind of activities related to technical and subsistence practices. The analytical developments of recent years, founded on the combination of naturalist (geology/ petrography) and archaeometric (mineralogical and elemental analysis) approaches, have provided a better understanding of the nature of these materials and allowed to investigate their geological origin. However, the application of these studies remains rare, even if colouring materials constitute an important potential of information for the understanding of technical and cultural behaviours, and the circulation of people and materials. There are several reasons for this scarcity of applications: 1/ the lack of knowledge about the evolutionary chains, i.e. the modifications of their characteristics due to bio-geochemical, anthropic and taphonomic transformations that occur from the deposit to their discovery: these modifications of their composition constitute biases that can limit the identification of the geological and geographical origin of the colouring materials; 2/ the diversity of the analytical protocols and the heterogeneity of data produced between laboratories and research teams: these biases limit the comparison of data between studies and limit the generalisation of these approaches; 3/ the difficulty of analysing and comparing the composition of blocks of colouring matter with that of residues on the surface of archaeological remains: while the protocols for analysing cohesive blocks are efficient and hardly invasive, the analysis of residues remains difficult and the analytical techniques used on the blocks do not provide the necessary spatial resolution for analysing these thin layers; 4/ the lack of robust geological references: the establishment of geological references at a regional or supra-regional scale requires considerable investment. The geological reference collections, established independently by researchers or teams as a result of projects centred on archaeological sites, are not easily accessible and reusable, notably because of standardisation issues. The objective of the Color-Sources project is to overcome these constraints in order to provide a new dynamic to the study of the origins of prehistoric colouring materials at a national and international scale, by developing and sharing knowledges and methodologies necessary to build geological reference collections and to compare them with archaeological collections. This objective will be achieved by developing an "open science" dynamic and the production of "FAIR" (Easy to Find, Accessible, Interoperable, Reusable) data. To this aim, Color-Sources will be supported by an interdisciplinary consortium in order a) to share the experience acquired in our various archaeological fields in order to better understand the evolutionary chains, to develop a common methodology for studying colouring materials and to implement it in a common field: the Dordogne and its periphery; b) to develop interoperable data acquisition protocols, to improve the statistical processing protocols for the data produced (particularly elementary data), and to develop an elementary analysis methodology by LA-ICP-MS/MS that could be applied to both blocks and residues of colouring materials in order to limit the biases induced by the use of several different techniques, c) to design an information system to save, reuse and disseminate the data acquired by the French community on the sources of raw colouring materials used in the Palaeolithic period.