Helianthemum bilyanense (Cistaceae), a new gypsum-halophytic specialist species from south-eastern Spain related to H. polygonoides

A new species, Helianthemum bilyanense (sect. Helianthemum), is described from a single population in gypsum saltmarshes of inland Alicante province (Comunidad Valenciana), in the south-eastern part of the Iberian Peninsula. It is closely related to H. polygonoides, but several differences in its general habit, floral pieces and indumentum of stem, fruit and seed allow easy recognition. Data on morphology, ecology, distribution and conservation are reported for the new species, and its taxonomic affinities are discussed based on phylogenetic analyses of the internal transcribed spacer region of nuclear ribosomal DNA. Due to the scarce number of individuals, the reduced area of occupancy and the existence of serious threats on the only know population, H. bilyanense is suggested; (i) to be labelled as CR according to the IUCN red list categories and (ii) to be included in the Spanish and the Valencian catalogues of threatened plant species as ‘threatened with extinction’.