Taxonomy,phytogeographyandethnobotany of the genus acalypha l. (euphorbiaceae) in Tanzania

Abstract

The genus Acalypha L. (Euphorbiaceae) represented by 28 species and 4 varieties in Tanzania has been investigated with respect to taxonomy by employing a wide range of taxonomic data, inclusive of cytology, palynology and taximetrics. Gaps on the phytogeography of Acalypha and frontiers of knowledge on the ethnobotany of the genus are reported. The study has resolved the taxonomic controversies of 12 problematical Acalypha species namely: A. boiviniana; A. braehystaehya; A. bussei, A. ciliata; A. engleri; A. fruticosa vars. fruticosa, eglandulosa, villosa; A. indica; A. lanceolata; A. neptunica vars. neptunica, vars. pubescens; A. paucifolia; A. psilostaehya vars. psilostachya, glandulosa and A. villicaulis. The study has also established a new record of the pollen morphology for 21 Acalypha species and 4 varieties, viz., A. acrogyna, A. ambigua, A. bipartita, A. braehystaehya, A. bussei, A. chirindica, A. echinus, A. engleri, A. gillmannii, A. hispida, A. laneeolata, A. neptuniea group, A. nyasica, A. ornata, A. paucifolia, A. psilostachya group, A. stuhlmalnii, A. villicaulis, A. volkensii, A. welwitschiana and A. wilkensiana. Of the 13 Acalypha taxa studied cytologically, the chromosome counts of 8 species are new records for genus Acalypha and include A. bipartita; A. chirindiea, A. fruticosa vars. fruticosa, eglandulosa and villosa; A. neptunica; A. villi eau lis and A. volkensii. Taximetric analyses as a modem taxonomic tool has enabled the establishment of a classification of the genus Acalypha L. in Tanzania based on the latest

(iii) infrageneric classification of the genus Acalypha by Pax and Hoffmann (1924). In my classification, the latter's subgenus Euacalypha and all the subsequent series, except series Oligogynae, have been retained. Their subgenus Linostachys has been dropped and the author's series Hypandre replaced by Section Monaxanthae Muell.Arg. In the classification, four Sections are proposed namely: (I) Polygynae- Pleurogynae, comprising 8 species and 1 variety in 7 series. (11) Pantogynae- Pleurogynae comprising 7 species and 3 varieties in 6 series. (Ill) Monaxanthae Muell. Arg., comprising 3 species in a single series and (IV) Pantogynae - Acrogynae, comprising 9 species in 4 series. On the basis of disjunct distribution pattern, Tanzanian Acalypha belong to 4 main categories namely, endemics (39.3%), moderates (42.4%), wides (12.1 %) and cultivated (6.2 %). The observed distribution pattern is dictated by altitude, edaphic factors, rainfall, temperature and vegetation types. Origin and evolution of Tanzanian Acalypha is associated with the disjunct afromontane regions and Lake Victoria regional mosaic area. The flowering period of Acalypha ranges from less than 6 months to throughout the year. Ethnobotanical studies have revealed that 71.0% of the Acalypha taxa have medicinal values and treat 46 human diseases and conditions, grouped as bacterial, viral, fungal, trypanosomal, molluscicidal, cytotoxins and protein synthesis inhibition. Also, 64.5 % of Acalypha taxa have other non-medicinal uses, VIZ., as vegetables, fodder, ornamentals and in

construction.