The Rare Moss Didymodon johansenii (R.S. Williams) H.A. Crum in the Italian and Austrian Alps

Abstract Didymodon johansenii (R.S. Williams) H.A. Crum is recorded for the first time for Italy from the Brenta Dolomites of the Southern Alps, Province of Trento. In addition, a series of unpublished records from the Austrian Alps are presented and the known distribution of the species in Central Europe is mapped. The differentiation of the species, which is well-characterized among European species by a swollen, deciduous leaf apex, is discussed. D. johansenii is a cryophilous xerophyte, usually growing in full sun on S-facing rock walls of limestone and calcareous schist in the subalpine and alpine belt of the Alps. It probably belongs to a series of bryophyte species with Central Asian origin which reached the Alps by crossing the cold steppes during the glacial maxima of the Pleistocene.