An assessment of the subgeneric classification of Zygophyllum (Zygophyllaceae) in Southern Africa : evidence from noncoding trnL-trnF chloroplast DNA sequences

Makwarela, Azwimpheleli M. (2001-04)

Thesis (M.Sc.(Systematics and Biodiversity Science))-- Stellenbosch University, 2001.


ENGLISH ABSTRACT: Sequence data from the intron and the spacer of the trnL-F chloroplast DNA region were used to study the phylogenetic relationships of the genus Zygophyllum L. (Zygophylloideae: Zygophyllaceae) in the southern African region. The chloroplast DNA was extracted from both herbarium and silica-gel dried material. Closely related genera, i.e. Augea Thunb., Fagonia L. and Tetraena Maxim. within the subfamily Zygophylloideae and more distantly related genera Seetzenia R.Br. ex Decne and Tribulus L. were used as outgroups. Sequences revealed length variation mainly due to the presence of indels (insertions and deletions). Phylogenetic analysis using parsimony revealed two distinct lineages for southern African members of Zygophyllum, corresponding to the proposed subgeneric classification (Van Huysteen 1937; Van Zyl 2000). There is a strong monophyly support for the sections within the subgenus Agrophyllum (Neck.) Endl. However, the transference of the monotypic section Grandifolia Engl. from subgenus Zygophyllum to Agrophyllum is not confirmed, because material of Z. stapffii Schinz. was not available. Despite the morphological evidence for the subdivision of the subgenus Zygophyllum, the molecular data did not confirm the monophyly for its sections. This could be the result of biased sampling, since all the species used in the analyses, except Z. cordifolium L.f. and Z. morgsana L., belong to section Capensia Engl. The trnL region data support the transfer of the mono typic section Morgsana Huysst. from subgenus Agrophyllum to subgenus Zygophyllum. The molecular data also seem to have implications for the biogeography of Zygophyllum. The southern African Agrophyllum representatives are related to East African and Middle East Zygophyllum species, whereas the southern African subgenus Zygophyllum members are closely related to Australian Zygophyllum species.

AFRIKAANSE OPSOMMING: Die volgorde-data van die trnL-F chloroplas-DNA gebied is gebruik om die filogenetiese verwantskappe van die genus Zygophyllum L. (Zygophylloideae: Zygophyllaceae) in suider Afrika te bestudeer. Die chloroplas-DNA is geëkstraheer van beide herbaria en silica-gel gedroogde materiaal. Naverwante genera binne die subfamilie Zygophylloideae bv. Augea Thunb., Fagonia L. en Tetraena Maxim., sowel as verder verwante genera, soos Seetzenia R.Br. ex Decne en Tribulus L., was as buite-groepe gebruik. Die lengte-variasie in die volgorde-data kan toegeskryf word aan indels (insertions and deletions). Filogenetiese analise deur die gebruik van parsimonie het twee duidelike ontwikkelingslyne vir suider-Afrikaanse Zygophyllum taksa aangedui. Dit stem goed ooreen met die voorgestelde subgeneriese klassifikasiesisteem vir die genus (Van Huysteen1937; Van Zyl 2000). Daar is 'n sterk ondersteuning vir monofilie van die seksies binne die subgenus Agrophyllum (Neck.) Endl. Die oorplasing van die monotipiese seksie Grandifolia Engl. vanaf subgenus Zygophyllum na subgenus Agrophyllum is nie bevestig nie, want materiaal van Z. stapffii Schinz. was nie beskikbaar nie. Ten spyte van morfologiese bewyse vir die subdivisie van die subgenus Zygophyllum het die molekulêre data nie die monofilie van die seksies bevestig nie. Dit is moontlik as gevolg van eensydige data-insameling, aangesien al die spesies wat in die analise gebruik word (behalwe Z. cordifolium L.f. en Z. morgsana L.) aan die seksie Capensia Engl. behoort. Die trnL-gebied data ondersteun die oordra van die monotipiese seksie Morgsana Huysst. van die subgenus Agrophyllum na die subgenus Zygophyllum. Die molekulêre data bied ode inligting oor die biogeografie van Zygophyllum. Die suider-Afrikaanse Agrophyllum taksa is verwant aan Oos-Afrika en Midde-Oosterse Zygophyllum spesies, terwyl lede van die Suid-Afrikaanse subgenus Zygophyllum nouverwant is aan Zygophyllum spesies in Australië.

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