Systematics Section / ASPT
Borg, Agneta Julia , McDade, Lucinda A. , Schönenberger, Jürg .
Molecular systematics and patterns of morphological evolution in Thunbergioideae (Acanthaceae).
THUNBERGIOIDEAE is one of three subfamilies within Acanthaceae. It consists of five genera, of which the major ones are Thunbergia (ca. 100 species in Africa and Asia), Mendoncia (ca. 60 species in Africa and tropical America), and Pseudocalyx (ca. 7 species in Africa). Due to superficial differences in the gynoecium, Mendoncia was often referred to its own subfamily or even family. Recent morphological and molecular studies, however, support the reduction to a single subfamily within Acanthaceae, but relationships within Thunbergioideae are still poorly understood. Thunbergioideae differ from other Acanthaceae mainly in their predominantly climbing habit, their reduced calyx, and their enlarged bracteoles. Differences in growth form, leaf and inflorescence characters, and floral structures have been the basis for a further division of the genus Thunbergia into eight subgenera. The present study reconstructs phylogenetic relationships of Thunbergioideae using molecular data from three chloroplast regions (rps16 and rpL16 introns and trnT-trnL intergenic spacer) and explores the evolution of growth form and floral structures based on these data. The results suggest that Mendoncia and Thunbergia are each monophyletic and that Pseudocalyx is sister to Thunbergia. Several strongly supported subclades within Mendoncia and Thunbergia can be identified, and earlier, morphology-based subgeneric divisions of Thunbergia are congruent with molecular evidence. Climbing growth form appears to be ancestral within Thunbergioideae and characterizes both Mendoncia and Pseudocalyx, while an erect growth form has evolved twice in Thunbergia. Reconstructions of the evolution of further morphological traits will be presented.[c.e.:srb]
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1 - Stockholm University, Department of Botany, Lilla Frescativägen 5, Stockholm, SE-10691, Sweden
2 - Academy of Natural Sciences, Department of Botany, 1900 Benjamin Franklin Parkway, Philadelphia, Pennsylvania, 19103, USA
Presentation Type: Oral Paper:Papers for Sections
Date: Monday, July 31st, 2006
Time: 8:45 AM