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Morphometrics and molecular phylogenetics of the continental African species of Angraecum section Pectinaria (Orchidaceae)

par Simo-Droissart, Murielle;Micheneau, Claire ;Sonke, Bonaventure ;Droissart, Vincent ;Plunkett, Gregory;Lowry II, Porter;Hardy, Olivier J. ;Stevart, Tariq
Référence Plant ecology and evolution, 146, 3, page (295-309)
Publication Publié, 2013

Article révisé par les pairs

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Résumé :

Background and aims - Recent molecular studies suggest the polyphyly of Angraecum and the unnaturalness of some of its sections, as exemplified by sect. Pectinaria, which has species in two wellseparated clades, one in Madagascar and the other in continental Africa. However, species delimitation among the five continental African members remained problematic due to morphological variability. In preparation for the taxonomic revision of this group, we used morphological and molecular data to re-assess the circumscription of each species, and to evaluate their monophyly and relationships to one another. Methods - A total of 59 alcohol-preserved specimens were used to perform multivariate analyses on 37 morphological characters. DNA sequences from one nuclear (ITS-1) and five plastid regions (matK, rps16, trnL-F, trnC-petN and ycf1) were analyzed using Parsimony and Bayesian methods. Key results - The morphometric study revealed five distinct morphospecies that correspond to the concepts of the currently recognized species. Angraecum doratophyllum and A. subulatum are the most distinct morphologically, whereas A. atlanticum, A. gabonense and A. pungens are most similar to one another. Phylogenetic analyses using a combined data set of the six markers yielded highly resolved, congruent trees with strong branch support. The polyphyly of A. sect. Pectinaria is confirmed, with continental African members appearing to be most closely related to sect. Dolabrifolia, found exclusively in Africa. The multiple accessions of A. doratophyllum, A. gabonense, A. pungens and A. subulatum each formed a well-supported clade. Parsimony and Bayesian analyses placed A. atlanticum and A. pungens in a subclade within which samples of A. pungens were nested but those of A. atlanticum formed a grade. These two species can be easily distinguished morphologically by leaf dimensions and flower length, but broader sampling in continental Africa is needed to test whether individuals recognized as A. atlanticum might represent two distinct taxa. © 2013 National Botanic Garden of Belgium and Royal Botanical Society of Belgium.