Using endemic-plant distribution, geology and geomorphology in biogeography: the case of Sardinia (Mediterranean Basin)

Abstract

The importance of robust systems for classifying biogeographical patterns has been emphasized for its usefulness in\ud designing conservation strategies. For such purposes, the distribution patterns of the endemic flora have often been used.\ud Several studies have identified phytogeographical units within Sardinia (western Mediterranean); however, the main part of\ud the island remains unstudied. Thus, the aim of this study is to lay out a comprehensive biogeographical scheme for Sardinia\ud based on endemic vascular plant distributions, together with geological and geomorphological units. We georeferenced, in\ud a 1-km2 grid cell, the presence of 290 vascular endemic taxa from the literature, herbarium specimens and field\ud investigators’ research. Sardinia was subdivided into 31 homogeneous units through the integration of geological and\ud geomorphological maps and, subsequently, a presence–absence matrix of endemic taxa in each unit was built. Hierarchical\ud cluster analysis was performed to define two levels of biogeographical units (i.e. sectors and subsectors). For each unit the\ud exclusive and differential endemic taxa were identified. For sectors, indicator species were explored by the Indicator Value\ud (Ind Val) analysis and relationships were analysed by quantitative interaction web. A total of six sectors and 22 subsectors\ud were identified. The highest endemic plant richness was found in the Campidanese-Turritano, Sulcitano-Iglesiente and\ud Supramontano sectors, and in the Gennargenteo, Barbaricino, Iglesiente and Sulcitano subsectors. All sectors were\ud characterized by the presence of exclusive, differential and indicator taxa. The interaction analysis showed the highest\ud uniqueness in endemic flora in the Supramontano and Sulcitano-Iglesiente sectors, which hosted a high number of\ud exclusive endemic species. Mostly mountainous sectors/subsectors had higher endemic-species richness compared with\ud lowland ones. The study showed the relevance of geology and geomorphology, together with accurate data on endemic\ud distribution, to define consistent phytogeographical units. Furthermore, the biogeographical scheme presented here helps to\ud define area-based conservation strategies in Sardini

Threatened Sardinian vascular flora: A synthesis of 10 years of monitoring activities

“…However, the endemic plant richness is not uniformly distributed, but depends largely on environmental conditions and, for this phenomenon, the endemism-rich areas at the regional level are defined as micro-hotspots . In Sardinia, three micro-hotspots are identified (Supramontes, Iglesiente, and Gennargentu; see the map in Cañ adas et al 2014); these micro-hotspots, corresponding to the biogeographic units defined by Fenu et al (2014), not only host more than 20% of regional endemics, but also a high number of narrow endemics (Fenu et al 2010;Cañ adas et al 2014).…”

“…Range: ENE, extremely narrow endemic; NE, narrow endemic; E, exclusive Sardinian endemic; PIPPs, peripheral and isolated plant populations. Chorology (Ch); Biogeographic sector (according toFenu et al 2014); Locality (Loc): in some cases correspond to the population.Representativeness rate (Rep.); Frequency (Freq. ):, number of monitoring per year.…”

Global and Regional IUCN Red List Assessments: 1

“…Ex situ gene resource banking is recommended, for possible plant translocation programmes aimed at increasing the very low number of individuals in the subpopulations. (Fenu et al 2014); its distribution consists of 14 populations located in Sardinian coastal environments and only one population in Corsica (Fig. 6).…”

Global and Regional IUCN Red List Assessments: 2

“…2). Until recently, C. glaucophylla was known only from the Sulcitano-Iglesiente biogeographic sector (Isola di San Pietro, Pranu Sartu, Is Arenas and Monte Linas; Fenu et al 2014). In recent years, this taxon was also discovered in three small localities in the mountainous inlands of Monte Limbara (north Sardinia).…”

“…Charybdis glaucophylla ( Fig. 1) is endemic to the Sardo-Corsican biogeographical province (Fenu et al 2014); its known distribution consists of seven populations in Sardinia and one population in Corsica (Fig. 2).…”