EPIFUN

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.