European fan palm (Chamaerops humilis L., Arecaceae) on the central and northern coast of Catalonia: native, introduced or reappeared?

Abstract

Chamaerops humilis L., the European fan palm, is the only native palm in the western Mediterranean basin. In Catalonia (north-western Iberian Peninsula), the Garraf Massif is generally regarded as its natural north distribution limit. According to old accounts, however, the species seems to have occurred in Montjuïc Mountain, Barcelona, from where it would have been extinct. Herein we are presenting the results of extensive fieldwork conducted during the last five years in order to (1) check whether the species is still persisting in Montjuïc, (2) explore whether this dwarf palm is also present in other areas of Catalonia further north of the Garraf not cited in the literature and, if so, to disentangle its biogeographic status (i.e., native or alien). We have been able to detect several populations in Montjuïc Mountain (with a population containing roughly a thousand individuals) close to cultivated plants. The youth of most individuals and their proximity to cultivated plants indicate that they are probably escapes. This might suggest that C. humilis is today present in an area that would be part of its historical range. This palm should be considered as introduced in the remaining locations where the species has been observed north to the Llobregat river. Notably, in most of these places C. humilis occurs as isolated individuals or as very small stands.