On the identity of Herbertus borealis (Jungermanniopsida: Herbertaceae), with notes on the possible origin of H-sendtneri

The assumed European endemic Herbertus borealis differs from the closely related Holarctic species H. aduncus and H. stramineus by the convex vitta, a strongly asymmetrical leaf lamina and the dorsal lobes being much broader than the ventral ones. The latter character recurs in Asian H. delavayi and tropical American H. acanthelius. Phylogenetic analyses of nrITS sequences resolve H. borealis from the British Isles in a robust monophyletic lineage with H. delavayi from Bhutan whereas H. acanthelius is placed in a separate clade. Based on the molecular topology and morphological comparisons we propose to lower H. borealis to a synonym of H. delavayi. Accessions of H. dicranus from Africa and Asia are placed sister to a robust clade with H. delavayi, H. stramineus and H. aduncus. A sequence of H. giraldianus is nested within H. dicranus, supporting an earlier view that a synonym of the polymorphic H. dicranus is at hand. Herbertus sendtneri from Malaysia is placed sister to a clade with H. sendtneri accessions from Austria, the Azores and tropical America in a robust sister relationship. Based on this topology we deduce an Asian origin of H. sendtneri.