Abstract/Summary

Bryophytes are critical components of many terrestrial ecosystems yet they are often understudied. This is especially true across sub-Saharan Africa and the Indian Ocean islands; a large region of similar floristic composition which encompasses several global hotspots for bryophyte diversity and endemism. The Orthotrichaceae is the fifth largest moss family in sub-Saharan Africa and these mosses form a conspicuous element of tropical montane forests, usually growing as epiphytes on trees. Across tropical Africa the family is most notably represented by Macromitrium and Schlotheimia; two large and problematic genera which have received little taxonomic attention in this region. The numerous superfluous names and lack of identification guides have been a serious impediment to floristic and ecological studies. The aim of this work has been to help address this taxonomic deficit by producing a comprehensive treatment of the Orthotrichaceae across tropical Africa and the Indian Ocean islands. Macromitrium as currently described is particularly diverse morphologically with 26 species now recognised within the study region. Preliminary molecular data presented here suggest the limits of Macromitrium will need to be revised to maintain a monophyletic classification, though more data are still needed to confirm generic boundaries. The main body of work has been dedicated to critical taxonomic assessment of names and determination of species limits based on the detailed microscopic examination of 290 nomenclatural types and 2,188 herbarium specimens from the study region. The work presented in this thesis has resolved problems of species delimitation and nomenclature. Forty-five superfluous names have been placed in synonymy and 35 new lectotypifications made to ensure a stable nomenclature for future researchers working on this group.