A revision of Leptogium (Collemataceae, lichenized Ascomycota) from Antarctica with a key to species

With more than 180 known species, Leptogium has its greatest richness in tropical regions. Only three species have so far been reported from Antarctica but extensive surveys in the Antarctic Maritime Islands have shown that this is an underestimate. Leptogium antarcticum (non-isidiate, with medulla composed of columnar hyphae), L. marcellii (non-isidiate, with medulla composed of a sponge-like arrangement of hyphae) and L. tectum (isidiate, with medulla composed of columnar hyphae) are described here as new to science. The new species are compared with those already reported for the genus in Antarctica, namely L. crispatellum, L. menziesii and L. puberulum, and an identification key is provided. Sequences of ITS and mrSSU regions were obtained from recently collected L. antarcticum, L. marcellii, L. puberulum and L. tectum specimens. Morphological and anatomical data were compared along with available genetic data in order to delimit these species more accurately, using an integrative approach.