Relict species and the challenges for conservation: the emblematic case of Zelkova sicula Di Pasquale, Garfì et Quézel and the efforts to save it from extinction

The foreseen rapid climate changes are thought to represent a major threat for many plant species. Owing to that, in the Mediterranean Basin, one the most important area worldwide for biodiversity, a number of taxa are at risk of extinction, especially the endemics and the rarest ones. Within them a particular significance is recognised to the pre-glacial relicts, that are rather conspicuous in the area and represent a valuable heritage for their biogeographical relevance and evolutionary history. Zelkova sicula is one of the most prominent plants within this flora. To date, it is a very rare species, and due to a number of threatening factors it is on the brink of extinction. In the present paper, we discuss the main topics related to its conservation criticalities and the ongoing integrated strategies to save it from extinction. Particular emphasis is addressed to assisted colonisation, a "last resort" conservation approach consisting in the establishment of pilot-planting out of the species native range.