Language: French with bilingual summary in English and French
The lichen inventory of the Canton of Geneva was undertaken based on three components: (a) field surveys realized between 2008 and 2013; {b) compilation of existing data and literature, and (c) search for specimens from the Canton deposited in the herbarium of Geneva. This study allowed gathering of ca. 17,000 records.
These data allow tracing back the progresses in lichenological knowledge of the Canton of Geneva from 1801 to 2013. Two important sources of unpublished data were discovered. Firstly, the abundant notes taken by Müller Argoviensis that he continued to gathered after his publication Énumération des lichens des Environs de Genève in 1862 until his death in 1896. Secondly, the lichen herbarium of Jacques Rome, with more than 1200 specimens collected in the Canton of Geneva between 1874 and 1887. All these unpublished data are presented in this work.
The first mention of a lichen species dates back to 1801. Müller Argoviensis cited 150 species in 1862 and probably knew more than 300 species in the Canton of Geneva by the end of his life in 1896. Philippe Clerc mentioned 283 known species in the Canton in the first Catalogue of the lichens of Switzerland in 2004. The present inventory listed more than 600 species.
The analysis of these results shows how the number of species has varied through time, and that some species have disappeared during the course of the last two centuries. Our surveys coupled with historical information allow tracking down the evolution of the lichens in a context of changes in their environment such as watersides, forests and urban habitats and especially in the context of acidic and azotic pollutions in the last 100 years.
A list of the phytosociological syntaxa that are quite likely to exist in the Canton is provided. Lichens are often linked to microhabitats and therefore highly contribute to the biodiversity of the Canton. The phytosociological alliances are presented in 16 forms with a description of their characteristics and with illustrations.