Syntaxonomy of a species of Community interest across the entire alpine range: the endemic Trifolium saxatile

Andrea Mainetti ¹, Ginevra Nota ², Michele Lonati ²

Andrea Mainetti, Gran Paradiso National Park ¹, DISAFA, University of Torino (IT) ²

Trifolium saxatile is an endemic species of the Alps, with a fragmented distribution split into two main areas: one in the Western Alps spanning Italy, France, and southwestern Switzerland, and another in the Eastern Alps between Tyrol and South Tyrol. Likely a relict species (Favarger 1989), it is listed in Annex II of the EU Habitats Directive , necessitating periodic monitoring and conservation commitments at the EU level. However, the habitat selection and phytosociological significance of this species remain debated. Some authors classified it as a characteristic species of alpine riverbed communities (Epilobion fleischeri according to Villaret et al. 2017, Epilobietalia fleischeri according to Grabherr and Mucina 1993). Others have proposed T. saxatile as characteristic of a new phytosociological association ranked in the alpine siliceous scree communities (Androsacion alpinae, Dellinger and Berger 2009). Nevertheless, this latter proposal is poorly defined phytosociologically, contested by some authors (Unterluggauer et al. 2013), and based on phytosociological surveys conducted in a limited portion of the species’ range in Austria. These findings raise the question of whether some of these habitats might represent the species' primary and original environments, while others could be secondary. This study aims to reassess the ecological significance of T. saxatile and comprehensively describe the habitats where it grows through a phytosociological study based on surveys encompassing the entire distribution range of the species, integrating published and original data. Thirty-five new phytosociological relevés were conducted in the Italian Western Alps, while publications and databases containing relevés from France (CBNA 2023), Switzerland (Richard 1989, Steiner 1999), Tyrol, and South Tyrol (Unterluggauer et al. 2013) were digitised. The nomenclature (following Bartolucci et al. 2024) and the abundance values were harmonised, resulting in a dataset comprising 128 phytosociological relevés. Abundance values were transformed into Van der Maarel scores (2007), and a cluster analysis (Bray-Curtis similarity; UPGMA algorithm) was performed on the entire database. Characteristic species at the alliance, order, and class levels were identified in accordance with Grabherr and Mucina (1993), integrated by Theurillat et al. (1994), for five different scree and grassland phytosociological classes. The phytosociological analysis across the species’ entire range confirmed the existence of distinct clusters, particularly in riverbed and alpine siliceous scree habitats. Among these, a well-defined cluster within the Androsacion alpinae alliance was identified, supporting the proposal of a new and distinctly defined association named Saxifrago bryoidis-Trifolietum saxatilis ass.nova. This new association suggests that alpine siliceous screes should be considered the primary habitat where the species has persisted, while riverbeds represent secondary habitats. These insights into the phytosociological framework of the species will better guide monitoring and conservation efforts for this species of conservation concern.

Main author career stage: Postdoc / Fellow

Contribution type: Talk

First choice session: 2. Ecology

Second choice session: 3. Biodiversity and global change