Sematophyllum rheophyticum (Bryopsida, Sematophyllaceae), a new rheophytic species from Rwanda

Abstract

Background: Sematophyllum is a pantropical genus of approximately 170 species. The genus
has never been revised on a global scale and is poorly known in many areas of the world. This
is perhaps especially true in Africa where 60 accepted species are recorded, many seemingly
endemic to the eastern and central tropical areas. Further taxonomic work will enable better
understanding of the genus, its biogeography and regional patterns of plant diversity; help
guide conservation efforts; and facilitate a broader understanding of the evolution of the Afrotropical
flora.
Objectives: The objective of this study is to describe a new species of Sematophyllum from
Rwanda, part of the mega-diverse Albertine Rift system.
Methods: Light microscopy was used to compare anatomical and morphological details of the
putative new species with specimens of other members of the genus with which it could
potentially be conspecific.
Results: Sematophyllum rheophyticum W.R. Buck & Hedd. was described as new and is currently
known only from the type locality at Gisakura, Nyungwe National Park, Rwanda. It is
distinguishable from all congeners by a unique combination of characters including the
concave, abruptly acuminate leaves, the alar areolation and the rheophytic habitat.
Conclusion: Sematophyllum rdicum is a new species, defined by a combination of several
anatomical characters, known currently only from the type locality. Furthermore, it is one of
only a few species in the genus that occurs in rheophytic habitats. Its phylogenetic relationships
are obscure and will probably need to be evaluated with molecular evidence.