Broad-ranged, highly disjunct, locally rare and severely endangered: the challenging risk assessment and a global conservation strategy for Ericasicula Guss. sensu lato (Ericaceae).

Abstract

The distribution range of Ericasicula Guss. sensu lato spans the central and eastern Mediterranean Basin, but shows a significantly fragmented pattern, and its populations are locally subject to multiple threats inducing continuous regression. The species is distributed across five countries, Italy, Libya, Cyprus, Türkiye and Lebanon, and includes two subspecies, subsp. sicula and subsp. bocquetii, currently represented by 31 and 8 stands, respectively. This study provides an updated overview of the distribution, ecology, and conservation status of both subspecies. New distribution data and ecological information were gathered through fieldwork, literature, and herbarium specimens. In Sicily (Italy), unmanned aerial systems and high-resolution digital elevation models were employed to perform a detailed census of the last extant stand, mapping its distribution and calculating its 3D occupation surface. Based on our analyses, Ericasicula is evaluated as Least Concern (LC) at the global level, even though each subspecies and subpopulation are nationally endangered. In fact, 19 locations of E.siculasubsp.sicula were not confirmed recently, and this subspecies should be considered as Critically Endangered (CR) in Italy and Vulnerable (VU) in Lebanon, Cyprus and Türkiye. In Libya, E.siculasubsp.sicula is VU due to severe habitat degradation. E.siculasubsp.bocquetii, formerly known from a few locations in the mountains of SW Anatolia, Türkiye, has been found at lower altitudes in several new locations and is also assessed as VU. Further fieldwork is recommended to better assess the demographic trends of the different subpopulations. Genetic analyses are needed to clarify the taxonomic value of infraspecific taxa previously described and to guide future conservation efforts of the most unique and genetically rich stands, both in-situ and ex-situ. Improving the conservation strategies for taxa like Ericasicula s. l. requires the collaboration of specialists from all involved countries, making it crucial to maintain networks of experts in the Mediterranean.