The census of the loci classici of 1,227 native, non-endemic vascular plants described from Italy is here presented and described. The effective place of publication of accepted names, basionyms and homotypic synonyms were identified and critically verified. The geographic information on the loci classici was excerpted from the protologues, as well as information on typification for the taxa described before 1 January 1958. The names without a holotype are 1,165. For 591 names a lecto- or neo-typification is available in literature, while 572 currently accepted taxa still need a type designation. For ten of these names showing previous ineffective typification, nomenclatural types are designated here (Allium savii, A. tenuiflorum, Anemone millefoliata, Catapodium tuberculosum, Cynosurus siculus, Filago congesta, Saponaria bellidifolia, Sclerochloa patens, S. zwierleinii, and Vicia leucantha). A new combination (Trisetaria aurea comb. nov.) is proposed. The general picture of the currently accepted taxa of vascular plants described from Italy, including endemics, amounts to 2,631, i.e. about 32% of the native flora currently recorded for the country.

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A syntaxonomical revision of the Isoëto-Nanojuncetea class for the Sicilian territory is provided. This syntaxon gathers the ephemeral herbaceous hygrophilous plant communities linked to periodically submerged soils, widely distributed in the European, circum-Mediterranean and Macaronesian territories. Within this class, two orders are recognized, lsoëtetalia, with a prevalently Mediterranean distribution, and Nanocyperetalia chiefly occurring in the central-European and Atlantic territories, with scattered and marginal occurrence in the Mediterranean area. The order Isoëtetalia in Sicily is represented by four alliances, i.e., Isoëtion, Preslion cervinae, Cicendio-Solenopsion laurentiae and Agrostion salmanticae, while within Nanocyperetalia three alliances can be recognized, namely Nanocyperion, Verbenion supinae and Lythrion tribracteati. Overall, 32 plant communities are recognized, 11 of which are described for the first time. Each higher rank syntaxa and related associations are examined from a nomenclatural, floristic, ecological and chorological point of view. In particular, the associations were processed using cluster analysis in order to highlight the correlations between them. Regarding the floristic aspects, a checklist of the species occurring in the phytosociological relevés is provided, as well as a new combination concerning Solenopsis gasparrinii, a critical species of the Sicilian flora, is proposed.

Background Altitudinal variation in vascular plant richness and endemism is crucial for the conservation of biodiversity. Territories featured by a high species richness may have a low number of endemic species, but not necessarily in a coherent pattern. The main aim of our research is to perform an in-depth survey on the distribution patterns of vascular plant species richness and endemism along the elevation gradient of Mt. Etna, the highest active volcano in Europe. Methods We used all the available data (literature, herbarium and seed collections), plus hundreds of original (G Giusso, P Minissale, S Sciandrello, pers. obs., 2010–2020) on the occurrence of the Etna plant species. Mt. Etna (highest peak at 3,328 mt a.s.l.) was divided into 33 belts 100 m wide and the species richness of each altitudinal range was calculated as the total number of species per interval. In order to identify areas with high plant conservation priority, 29 narrow endemic species (EE) were investigated through hot spot analysis using the “Optimized Hot Spot Analysis” tool available in the ESRI ArcGIS software package. Results Overall against a floristic richness of about 1,055 taxa, 92 taxa are endemic, of which 29 taxa are exclusive (EE) of Mt. Etna, 27 endemic of Sicily (ES) and 35 taxa endemic of Italy (EI). Plant species richness slowly grows up to 1,000 m, then decreases with increasing altitude, while endemic richness shows an increasing percentage incidence along the altitudinal gradient (attributed to the increased isolation of higher elevation). The highest endemic richness is recorded from 2,000 up to 2,800 m a.s.l., while the highest narrow endemic richness (EE) ranges from 2,500 up to 2,800 m a.s.l. Life-form patterns clearly change along altitudinal gradient. In regard to the life-form of the endemics, the most represented are the hemicryptophytes, annual plants (therophytes) are prevailing at lower altitudes and show a decreasing trend with increasing elevation, while chamaephytes are featured by an increasing trend up to 3,100 m of altitude. Furthermore, the results of the hotspot analysis emphasize the high plant conservation priority areas localized in oro-mediterranean (1,800–2,400 m s.l.m.) and cryo-mediterranean (2,400–2,800 m) bioclimatic belts, in correspondence of the oldest substrates of the volcano. Conclusions High plant speciation rate caused by increasing isolation with elevation is the most plausible explanation for the largest active volcano in Europe. The high degree of endemic species on Mt. Etna is linked to its geographical, geological and climatic isolation, all important drivers of speciation acting on the population gene flows. The hot spot map obtained represents a useful support for help environmental decision makers to identify priority areas for plant conservation.