First finding in Sicily of Bidens subalternans (Asteraceae).

It is reported the presence in Sicily of a new alien species destined to a progressive further spread in the Island. It is Bidens subalternans DC., an annual asteracea of American origin, already known in other Italian regions (Friuli Venezia Giulia, Lombardia, Marche, Lazio and Campania) and in other European countries (Belgium, Corse, Croatia, Cyprus, France, Germany, Great Britain, Montenegro, Republic of Serbia, Slovenia, Spain, Switzerland). The new locality, in Sicily, occurs along the roadside Monreale -- Pioppo, south of the city of Palermo. In this station, B. subalternans is found together with B. pilosa subsp. minor and other indigenous and exotic nitrophilous taxa. The population observed near Monreale (Palermo), is quite large and, according to the methods of dispersion, shows in Sicily an invasive tendency in favourable environment. The affinities of B. subalternans with B. bipinnata L. -- with which the species was sometimes confused -- is also discussed. [ABSTRACT FROM AUTHOR]