Journal Article

Molecular phylogenies disprove a hypothesized C<sub>4</sub> reversion in <i>Eragrostis walteri</i> (Poaceae)

Amanda L. Ingram, Pascal-Antoine Christin and Colin P. Osborne

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 107, issue 2, pages 321-325
Published in print February 2011 | ISSN: 0305-7364
Published online November 2010 | e-ISSN: 1095-8290 | DOI: http://dx.doi.org/10.1093/aob/mcq226
Molecular phylogenies disprove a hypothesized C4 reversion in Eragrostis walteri (Poaceae)

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  • Ecology and Conservation
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Background and Aims

The main assemblage of the grass subfamily Chloridoideae is the largest known clade of C4 plant species, with the notable exception of Eragrostis walteri Pilg., whose leaf anatomy has been described as typical of C3 plants. Eragrostis walteri is therefore classically hypothesized to represent an exceptional example of evolutionary reversion from C4 to C3 photosynthesis. Here this hypothesis is tested by verifying the photosynthetic type of E. walteri and its classification.

Methods

Carbon isotope analyses were used to determine the photosynthetic pathway of several E. walteri accessions, and phylogenetic analyses of plastid rbcL and ndhF and nuclear internal transcribed spacer DNA sequences were used to establish the phylogenetic position of the species.

Results

Carbon isotope analyses confirmed that E. walteri is a C3 plant. However, phylogenetic analyses demonstrate that this species has been misclassified, showing that E. walteri is positioned outside Chloridoideae in Arundinoideae, a subfamily comprised entirely of C3 species.

Conclusions

The long-standing hypothesis of C4 to C3 reversion in E. walteri is rejected, and the classification of this species needs to be re-evaluated.

Keywords: C4 photosynthesis; evolution; reversion; Eragrostis; Chloridoideae; Arundinoideae; Poaceae; Africa; Namibia

Journal Article.  2528 words.  Illustrated.

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

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