Linaria almadensis (Plantaginaceae, Antirrhineae): a highly threatened new toadflax endemic to the Tagus mouth cliffs, opposite Lisbon (Portugal)

Abstract

A new species of Linaria subsect. Supinae is described from the Tagus mouth cliffs (TMC), located about 2 km south of Lisbon, in the municipality of Almada. The taxonomic treatment, including a key to morphologically allied species, is followed by a report on the vegetation of the TMC. Linaria almadensis, historically identified as L. glaucophylla, L. marginata, L. tristis, L. polygalifolia, L. aeruginea, and L. supina, is endemic to these coastal cliffs, formed during the Pleistocene, where it grows on sandy walls in the vicinity of carbonate rocks. It is associated with a chasmo-chomophytic community including some Portuguese endemics (Silene long-icilia) or near-endemics (i.e. Antirrhinum linkianum, Calendula suffruticosa subsp. lusitanica), requiring legal protection under Annex I to the Habitats Directive. Linaria almadensis is most similar to L. tristis subsp. marginata, and L. supina s.l. from which it differs by the narrowly elliptic-oblong to elliptic-oblanceolate leaves, with an obtuse-apiculate apex, and the wider corolla tube in lateral section. Bees of the genus Anthophora are here reported as pollinators of L. almadensis, and evolutionary hypotheses for its origin are discussed. Due to its restricted distribution and pressing threats to its habitat, including invasive species and infrastructural encroachment, L. almadensis is preliminarily red-listed as Critically Endangered. The existence of a narrow endemic on the brink of extinction, one priority habitat at the European level, and a rich geological heritage in the TMC, call for the urgent definition of a new protected area in one of the most densely inhabited areas of Europe. ARTICLE HISTORY