A revision of African Velloziaceae based on leaf anatomy characters and rbcL nucleotide sequences

The African Velloziaceae is revised mainly using evidence from leaf anatomy and rbcL sequence data. Xerophyta is the only African genus in the family. Forty-five species are recognized in Africa, 11 of which are described as new and distinct on the basis of morphological, anatomical and/or genetic characters; one species is known to occur on the Arabian Peninsula, and 25 species are presently identified in Madagascar. The leaf anatomy of all Xerophyta spp. and the rbcL sequences of 44 Xerophyta spp. are examined. Four distinct types of leaf anatomy are (re-)defined and, with additional anatomical and morphological features, are used to produce a key to African Xerophyta. For each species, the morphology, leaf anatomy, synonymy, distribution, extensive literature sources and specimens used are given. The combined anatomical/genetic evidence allowed the description of the new species and the definition of X.simulans as singular in African Velloziaceae with leaf anatomical similarities to the South American Vellozia plicata and to Cyclanthaceae. The analysis of the rbcL sequence data supports the Chinese genus Acanthochlamys as sister to Velloziaceae s.s., the monophyly of the Old Word genus Xerophyta and its separation from the New World taxa. In Xerophyta, a well-supported clade includes all species with radial isolateral mesophyll (Barbacenia-type leaf anatomy). The other leaf types do not separate into uniform clades. A Madagascan clade houses species with Vellozia- and Xerophyta-type leaf anatomy and also contains the pan-African X.humilis. (c) 2013 The Linnean Society of London