Panayotis Dimopoulos, Gianluigi Bacchetta, Zoltán Barina, Juan Arroyo, Vlado Matevski, Gianniantonio Domina, Anne-Christine Monnet, Frédéric Médail, Daniel Pavon, Bruno Fady, Toni Nikolić, Marwan Cheikh Albassatneh, Stephen Mifsud, Agathe Leriche, Institut méditerranéen de biodiversité et d'écologie marine et continentale (IMBE), Avignon Université (AU)-Aix Marseille Université (AMU)-Institut de recherche pour le développement [IRD] : UMR237-Centre National de la Recherche Scientifique (CNRS), Faculty of Science [Zagreb], University of Zagreb, University of Patras, Università degli Studi di Cagliari = University of Cagliari (UniCa), Dept. de Biologia Vegetal y Ecologia, Universidad de Sevilla / University of Sevilla, Department of Botany, Hungarian Natural History Museum (Magyar Természettudományi Múzeum), Institut d'écologie et des sciences de l'environnement de Paris (iEES Paris), Institut National de la Recherche Agronomique (INRA)-Sorbonne Université (SU)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS), Università degli studi di Palermo - University of Palermo, Unité de Recherches Forestières Méditerranéennes (URFM), Institut National de la Recherche Agronomique (INRA), Macedonian Academy of Sciences and Arts [Skopje, North Macedonia] (MASA), EcoGozo, Regional Development Directorate - Ministry for Gozo, ANR-11-LABX-0061, ANR-11-IDEX-0001,Amidex,INITIATIVE D'EXCELLENCE AIX MARSEILLE UNIVERSITE(2011), Department of Biology, Division of Plant Biology, Laboratory of Botany, University of Patras, Centro Conservazione Biodiversità, Dipartimento di Scienze della Vita e dell’Ambiente, Università degli Studi di Cagliari, University of Sevilla, Department of Agriculture, Food and Forest Sciences, University of Palermo, Centre National de la Recherche Scientifique (CNRS)-Institut de recherche pour le développement [IRD] : UMR237-Aix Marseille Université (AMU)-Avignon Université (AU), Faculty of Science, University of Zagreb, Institut d'écologie et des sciences de l'environnement de Paris (IEES (UMR_7618 / UMR_D_242 / UMR_A_1392 / UM_113) ), Macedonian Academy of Sciences and Arts, ANR-11-IDEX-0001-02/11-LABX-0061,OTMed,Objectif Terre : Bassin Méditerranéen(2011), Universidad de Sevilla. Departamento de Biología Vegetal y Ecología, Médail, Frédéric, Monnet, Anne-Christine, Pavon, Daniel, Nikolic, Toni, Dimopoulos, Panayoti, Bacchetta, Gianluigi, Arroyo, Juan, Barina, Zoltán, Albassatneh, Marwan Cheikh, Domina, Gianniantonio, Fady, Bruno, Matevski, Vlado, Mifsud, Stephen, Leriche, Agathe, and University of Patras [Patras]
Background: Tree species represent 20% of the vascular plant species worldwide and they play a crucial role in the global functioning of the biosphere. The Mediterranean Basin is one of the 36 world biodiversity hotspots, and it is estimated that forests covered 82% of the landscape before the first human impacts, thousands of years ago. However, the spatial distribution of the Mediterranean biodiversity is still imperfectly known, and a focus on tree species constitutes a key issue for understanding forest functioning and develop conservation strategies. Methods: We provide the first comprehensive checklist of all native tree taxa (species and subspecies) present in the Mediterranean-European region (from Portugal to Cyprus). We identified some cases of woody species difficult to categorize as trees that we further called “cryptic trees”. We collected the occurrences of tree taxa by “administrative regions”, i.e. country or large island, and by biogeographical provinces. We studied the species-area relationship, and evaluated the conservation issues for threatened taxa following IUCN criteria. Results: We identified 245 tree taxa that included 210 species and 35 subspecies, belonging to 33 families and 64 genera. It included 46 endemic tree taxa (30 species and 16 subspecies), mainly distributed within a single biogeographical unit. The countries with the highest tree richness are Greece (146 taxa), Italy (133), Albania (122), Spain (155), Macedonia (116), and Croatia (110). The species-area relationship clearly discriminated the richest central-eastern (Balkans) and northern (Alpine and Cevenno-Pyrenean) biogeographical provinces, against the five western provinces in the Iberian Peninsula. We identified 44 unrecognized “cryptic trees”, representing 21% of the total trees. Among the 245 taxa identified, 19 are considered to be threatened (15 CR + EN + VU) or near threatened (4 NT) by IUCN. Conclusions: The Mediterranean-European region includes an unsuspectedly high number of tree taxa, almost 200 tree taxa more than in the central European region. This tree diversity is not distributed evenly and culminates in the central-eastern part of the Mediterranean region, whereas some large Tyrrhenian islands shelter several narrow endemic tree taxa. Few taxa are recognized as threatened in the IUCN Red list, and the vulnerability of these species is probably underestimated. French Foundation for Research on Biodiversity (FRB). Centre for Synthesis and Analysis of Biodiversity data ANR-11-LABX-0061