Journal Article

Phylogeny, evolutionary trends and classification of the <i>Spathelia</i>–<i>Ptaeroxylon</i> clade: morphological and molecular insights

M. S. Appelhans, E. Smets, S. G. Razafimandimbison, T. Haevermans, E. J. van Marle, A. Couloux, H. Rabarison, M. Randrianarivelojosia and P. J. A. Keßler

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 107, issue 8, pages 1259-1277
Published in print June 2011 | ISSN: 0305-7364
Published online June 2011 | e-ISSN: 1095-8290 | DOI: http://dx.doi.org/10.1093/aob/mcr076
Phylogeny, evolutionary trends and classification of the Spathelia–Ptaeroxylon clade: morphological and molecular insights

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Background and Aims

The SpatheliaPtaeroxylon clade is a group of morphologically diverse plants that have been classified together as a result of molecular phylogenetic studies. The clade is currently included in Rutaceae and recognized at a subfamilial level (Spathelioideae) despite the fact that most of its genera have traditionally been associated with other families and that there are no obvious morphological synapomorphies for the clade. The aim of the present study is to construct phylogenetic trees for the SpatheliaPtaeroxylon clade and to investigate anatomical characters in order to decide whether it should be kept in Rutaceae or recognized at the familial level. Anatomical characters were plotted on a cladogram to help explain character evolution within the group. Moreover, phylogenetic relationships and generic limits within the clade are also addressed.

Methods

A species-level phylogenetic analysis of the SpatheliaPtaeroxylon clade based on five plastid DNA regions (rbcL, atpB, trnL–trnF, rps16 and psbA–trnH) was conducted using Bayesian, maximum parsimony and maximum likelihood methods. Leaf and seed anatomical characters of all genera were (re)investigated by light and scanning electron microscopy.

Key Results

With the exception of Spathelia, all genera of the SpathelilaPtaeroxylon clade are monophyletic. The typical leaf and seed anatomical characters of Rutaceae were found. Further, the presence of oil cells in the leaves provides a possible synapomorphy for the clade.

Conclusions

The SpatheliaPtaeroxylon clade is well placed in Rutaceae and it is reasonable to unite the genera into one subfamily (Spathelioideae). We propose a new tribal classification of Spathelioideae. A narrow circumscription of Spathelia is established to make the genus monophyletic, and Sohnreyia is resurrected to accommodate the South American species of Spathelia. The most recent common ancestor of Spathelioideae probably had leaves with secretory cavities and oil cells, haplostemonous flowers with appendaged staminal filaments, and a tracheidal tegmen.

Keywords: Rutaceae; Sapindales; Spathelioideae; Spathelia–Ptaeroxylon clade; Sohnreyia; molecular phylogeny; leaf anatomy; seed coat anatomy

Journal Article.  11839 words.  Illustrated.

Subjects: Ecology and Conservation ; Evolutionary Biology ; Plant Sciences and Forestry

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