The validity of currently recognised sectional limits within Combretum Loefling, subgenus Combretum (Combretaceae) in Southern Africa.

Abstract

Taxonomic confusion associated with Combretum Loefling, subgenus Combretum (Combretaceae) resulted in this investigation into the validity of sectional limits within the subgenus in southern Africa. Eight sections, together with their species and infraspecific taxa, totalling 29, are currently recognised in this region. Light and scanning electron microscopy on herbarium samples representing the taxa concerned were used to observe a final total of 171 selected characters. Data from individual specimens were collected numerically and processed to produce phenograms using Rohlf's NTSYS-pc program; also to produce descriptions in natural language format. A data processing program, TAXON, was specially designed and implemented to facilitate the desired processing and output. With the possible exceptions of Macrostigmatea and Ciliatipetala which require further investigation before certainty is reached, currently recognised sections were found to be valid and the limits between them acceptable. The main sources of confusion in this subgenus were found to lie in certain currently recognised species and their infraspecific taxa. These taxa were observed not to be distinct. The status of non-distinct species has been changed whenever clear evidence exists in favour of these changes. Other changes to species and infraspecific taxa have been recommended, but only to be implemented if supportive evidence is found after further investigations. Changes of status have been made in section Angustimarginata Engl. & Diels, where C. caffrum (Eckl. & Zeyh.) Kuntze and C. woodii Dummer have become synonyms of C. erythrophyllum (Burch.) Sond., and C. vendae Van Wyk has become a subspecies of C. erythrophyllum (Burch.) Sond., i.e. ssp. vendae (Van Wyk) Rodman comb. & stat. nov. (ined.); and in section Spathulipetala Engl. & Diels, where C. mkuzense Carr & Retief ,(section Macrostigmatea Engl. & Diels) has become a synonym of C. zeyheri Sond. C. collinum ssp. gazense (Swynn. & Bak.F.) Okafor, section Metallicum Fresen., has been changed to C. collinum ssp. coriaceum (Schinz) Rodman (ined.) in accordance with international botanical nomenclature.