The impact of the invasive Kalanchoe ×houghtonii on vegetated sea cliffs of the Mediterranean coasts with endemic Limonium species

Abstract Invasive alien plant species threaten biodiversity, especially in ecologically rich regions such as the Mediterranean Basin. Coastal communities, which host many endemic taxa, are among the most affected. One such invasive taxon is Kalanchoe ×houghtonii, an allegedly artificial hybrid that, despite strong invasive potential, remains largely unrecognised as a taxon of concern in Mediterranean countries. In this study, we assess its impact on the Habitat of Community Interest “Vegetated sea cliffs of the Mediterranean coasts with endemic Limonium spp.” at two sites along the southern coast of Catalonia (NE Iberian Peninsula). We conducted fieldwork to document population size, growth stages, and spatial overlap with native species. Our results show that K. ×houghtonii form dense monospecific patches that apparently compete for space with two native Limonium species in southern Catalonia. We also gathered 723 iNaturalist occurrences of K. ×houghtonii to map its Mediterranean distribution, confirming the presence of this taxon in 107 Natura 2000 protected sites, 58 of them within this specific protected coastal habitat. Niche modelling indicates high climatic suitability of K. ×houghtonii across Mediterranean Natura 2000 sites containing this particular habitat, as well as substantial overlap with Mediterranean Limonium spp. occurrences obtained from iNaturalist. These findings highlight the invasive potential of K. ×houghtonii and support its inclusion in national catalogues of invasive species across Mediterranean countries, calling for systematic monitoring of its spread and ecological impacts.