J Syst Evol ›› 2024, Vol. 62 ›› Issue (2): 242-256.DOI: 10.1111/jse.13034

• Research Articles • Previous Articles     Next Articles

Plant species richness hotspots and related drivers across spatial scales in small Mediterranean islands

Riccardo Testolin1,2,3*, Fabio Attorre4, Vanessa Bruzzaniti1,2,3, Riccardo Guarino5, Borja Jiménez-Alfaro6, Michele Lussu1,2,3, Stefano Martellos2,7, Michele Di Musciano1,8, Salvatore Pasta9, Francesco Maria Sabatini1,10, Francesco Santi1, Piero Zannini1,2,3, and Alessandro Chiarucci1   

  1. 1 BIOME Lab, Department of Biological, Geological and Environmental Sciences, Alma Mater Studiorum University of Bologna, 40126 Bologna, Italy;
    2 Centro Interuniversitario per la Biodiversità Vegetale Big Data-PLANT DATA, Department of Biological, Geological and Environmental Sciences, Alma Mater Studiorum University of Bologna, 40126 Bologna, Italy;
    3 LifeWatch Italy, Lecce, Italy;
    4 Department of Environmental Biology, Sapienza University of Rome, 00185 Rome, Italy;
    5 Department of Biological, Chemical and Pharmaceutical Sciences and Technologies(STEBICEF), University of Palermo, 90128 Palermo, Italy;
    6 Biodiversity Research Institute(Univ. Oviedo-CSIC-Princ. Asturias), University of Oviedo, Campus de Mieres, 33600 Mieres, Spain;
    7 Department of Life Sciences, University of Trieste, 34128 Trieste, Italy;
    8 Department of Life, Health and Environmental Sciences, University of L'Aquila, 67100 L'Aquila, Italy;
    9 Institute of Biosciences and BioResources(IBBR), Italian National Research Council(CNR), Unit of Palermo, 90129 Palermo, Italy;
    10 Faculty of Forestry and Wood Sciences, Czech University of Life Sciences Prague, 165 00 Praha, Czech Republic
    *Author for correspondence. E-mail:riccardo.testolin@gmail.com
  • Received:2023-05-11 Accepted:2023-10-09 Online:2023-11-27 Published:2024-03-01

Abstract: Small islands represent a common feature in the Mediterranean and host a significant fraction of its biodiversity. However, the distribution of plant species richness across spatial scales—from local communities (alpha) to whole islands (gamma)—is largely unknown, and so is the influence of environmental, geographical, and topographical factors. By building upon classic biogeographic theory, we used the species–area relationship and about 4500 vegetation plots in 54 Central Mediterranean small islands to identify hotspots of plant species richness and the underlying spatial determinants across scales. To do so, we fitted and averaged eight species–area models on gamma and alpha richness against island area and plot size, respectively. Based on positive deviations from the fitted curves, we identified 12 islands as cross-scale hotspots. These islands encompassed around 70% of species and habitat richness, as well as almost 50% of the rarest species in the data set, while occupying less than 40% of the total island surface. By fitting generalized linear mixed models, we found that gamma richness was mainly explained by island area and was weakly related to mean annual temperature (positively) and annual precipitation (negatively). As for alpha richness, after accounting for the idiosyncratic effect of habitats and islands, plot size and gamma richness remained the only significant predictors, showing a positive relationship. This work contributes to the understanding of the patterns and drivers of plant diversity in Central Mediterranean small islands and outlines a useful methodology for the prioritization of conservation efforts.

Key words: biodiversity hotspots, conservation biogeography, species–area relationship, vascular plants, vegetation plots