Helianthemum sicanorum ( Cistaceae ) , a new species from Sicily

Brullo, S., Giusso del Galdo, G.P. & Sciandrello, S. 2007. Helianthemum sicanorum (Cistaceae), a new species from Sicily. Anales Jard. Bot. Madrid 64(1): 47-53. Helianthemum sicanorum, an endemic species occurring on calcareous marls near Gela (S Sicily), is described and illustrated. Due to its habit and flower morphology, H. sicanorum shows close relationships with H. kahiricum Del., circumscribed to the semi-arid habitats of northern Africa and the Middle East. H. sicanorum is quite rare and localized on steep slopes facing the sea, where it is a member of thermophilous garigues of the Cisto-Micromerietea class.


Introduction
The coastal belt of southern Sicily represents a very important area from the phytogeographical point of view.In fact, this part of the island is characterized by the occurrence of several endemic or rare species, mostly circumscribed to this territory (Giusso del Galdo & Sciandrello, 2003).During floristic investigations along the rocky coast of "Torre Manfria" (Gela), a small population of a really peculiar and hitherto uncollected Helianthemum was found (Proctor & Heywood, 1968;Pignatti, 1982).Based on investigations carried out on herbarium material (CAT, FI, RO) and literature data, this plant is closely related to H. kahiricum Delile, a xerophyte distributed in arid and semi-arid habitats of N Africa and the Middle East, but not recorded for any European country.However, the Sicilian population, differing from the typical of H. kahiricum in many morphological features chiefly concerning the leaves, inflorescence, flowers and fruits, is here described as a species new to science.
Etymology.The specific epithet refers to "Sicani", an ancient civilization settled in Sicily from the second millennium to the fifth century B.C.
Distribution.This species is known only for a small population of no more than 50 individuals, circumscribed to Torre Manfria near Gela, (S Sicily), along a narrow strip of rocky coast.
Habitat.Helianthemum sicanorum grows on Pliocenic marly limestones facing the sea, where it colonizes steep and hardly reachable slopes (Fig. 3).From the bioclimatic viewpoint the area at issue belongs to the bioclimatic belt with a lower thermo-Helianthemum sicanorum, a new species from Sicily mediterranean thermotype and upper semiarid ombrotype (Brullo & al. 1996).This species plays an important physiognomic role within the thermophilous garigues characterized by undersized chamaephytes linked to really arid habitats.In particular, it is a member of the Diplotaxio crassifoliae-Reaumurietum vermiculatae (Table 1), a xeric plant community described by Brullo & al. (2000) belonging to the Cisto-Micromerietea class.Within this association, some North African species (Reaumuria vermiculata L., Diplotaxis crassifolia (Rafin.)DC., etc.), usually rare for the Sicilian flora, are frequent too.
Phenology: flowering February to July; fruiting April to August.
Conservation status.At present, H. sicanorum is a threatened species at high risk of extinction as a result of the low number of individuals (less than 50) circumscribed to a narrow stand close to the sea.Therefore, since this species is seriously endangered by several human activities (such as tourist facilities, fire, urban sprawl, agricultural exploitation, and so on), we deem it should be added to the Regional Red List of Threatened Species as critically endangered (CR).
In conclusion, H. sicanorum represents an endemic with thermo-xerophilous requirements, showing a punctiform distribution area, which is likely to be the result of the long geographic isolation of the Sicilian population from the southern Mediterranean ones.