A critical evaluation of the Italian distribution of the rare macrolichen Usnea longissima Ach.

Abstract

The Italian distribution of the rare boreal–circumpolar macrolichen Usnea longissima is revised on the basis of a critical re-evaluation of bibliographic and field data. Reported from all Alpine regions of Italy, the species presently survives only in two neighbouring Alpine valleys of Friuli and Veneto. The Friulian population consists of a few thalli on a single tree near the lake of Sauris, while in Veneto scattered populations were observed in nine stands of Val Visdende with ca. 200 colonised trees. The species seems to be locally extinct in Trentino-Alto Adige. Earlier records from Lombardy, Piedmont and Aosta Valley are wrong or at least questionable. Usnea longissima can be considered as critically endangered at the national level. Some recommendations for forest managers are proposed.