A Revision of the Monotypic Genera Indusiella, Aligrimmia and Coscinodontella (Musci: Grimmiaceae), with Comments on Convergent Xeromorphological Features

Abstract

Indusiella thianschanica Broth. & C. Mifll., previously known from southern U.S.S.R., Mongolian People's Republic, Tibet, and Chad, occurs in North America in Alaska, U.S.A. Indu- siella andersonii Delgadillo is a synonym of I. thianschanica. The related Peruvian monotypic genera Aligrimmia and Coscinodontella are considered generically distinct from Indusiella. Con- vergent features include the elaboration oflaminal photosynthetic tissue such as occurs in Pottiaceae (some Pseudocrossidium, Tortula and Barbula species) and which is known in Grimmiaceae only in Indusiella. The highly disjunct occurrence of Indusiella in Alaska, outside its general range in mountainous desert and steppe regions of Asia and northern Africa, supports the hypothesis that more widespread steppe vegetation and aeolian deposits (sand deserts) occurred in Alaska during the cold, dry Duvanny Yar interval in late Pleistocene and that desert-steppe plants were more widespread in Beringia prior to climatic change and onset of the Holocene.