Systematic Studies In Rothmannia Sensu Lato Rubiaceae And A Revision Of The Malesian Taxa

Author : Joan Teresa Pereira
Publisher :
ISBN 13 :
Total Pages : 448 pages
Book Rating : 4.:/5 (847 download)

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Download or read book Systematic Studies in Rothmannia Sensu Lato (Rubiaceae) and a Revision of the Malesian Taxa written by Joan Teresa Pereira and published by . This book was released on 2008 with total page 448 pages. Available in PDF, EPUB and Kindle. Book excerpt: A review of the Southeast Asian, in particular the Malesian, species of Rothmannia Thunb. was undertaken. This considered not only the type and other species from Africa but also the closely related genera, Heinsenia (African) and Kochummenia (Malaysian). Parallel studies on the macromorphology, lower leaf surface micromorphology and palynology identified characters for group or species recognition within the Rothmannia complex. These indicated two highly distinctive groups, the African type species and alliance with right-contorted corolla lobes (Rothmannia s.s.) and two species placed within Kochummenia. Concurrently, two taxa were found morphologically aberrant within the genus as they have branch leaves in pairs or completely reduced, in contrast to most members of the Rothmannia complex, where branch leaves occur in trifoliate groups as a consequence of the nodes being very close together. One of these, R. macrophylla, a West Malesian endemic, was distinguished based on a different branch system with large pollen size, whereas the African R. globosa was out of place by its non-modular branch development and exclusively granular cuticular ornamentation on the lower leaf surface. The remaining species from Africa, across Asia and the SW Pacific were morphologically diverse but lacked a clear suite of unifying characters. The morphological characters of the Rothmannia complex were cladistically analysed and a limited molecular analysis was also carried out using the chloroplast trnQ-rps 16 intergenic spacer region. Results from both analyses suggest that Rothmannia is probably paraphyletic. Also, the relationships of the related taxa, Kochummenia and Heinsenia to other members within the complex could not be ascertained. Hence, the taxonomic delimitation of Rothmannia Thunb. remains unresolved. Nevertheless, the African type species and its alliance of related species with right-contorted corolla lobes can be considered Rothmannia in its strict sense (Rothmannia s.s.). In spite of the lack of clear resolution cladistically in the present work, the two related taxa, Kochummenia and Heinsenia will remain in their current circumscription because they have a number of distinctive characters, they are validly named genera, and only a wider-scope cladistic analysis including more genera in the tribe will be truly confirmatory. All the other species of Rothmannia (including the Malesian species) are best referred to as Rothmannia in its wider sense (Rothmannia s.l.). Inclusion of a wider representation of genera within the Gardenieae in a molecular analysis and, perhaps, a combined cladistic analysis of both morphological and molecular characters may be the best option for resolving these taxonomic uncertainties. A taxonomic enumeration of the Malesian species of Rothmannia s.l. revealed 18 species, including 11 combinations needed, five new species and one new variety to be proposed. Of these, 17 species are endemic to Malesia.