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The polyphyletic genus Sebaea (Gentianaceae: a step forward in understanding the morphological and karyological evolution of the Exaceae


Kissling, J; Yuan, Y M; Küpfer, P; Mansion, G (2009). The polyphyletic genus Sebaea (Gentianaceae: a step forward in understanding the morphological and karyological evolution of the Exaceae. Molecular Phylogenetics and Evolution, 53(3):734-748.

Abstract

Within the Gentianaceae-Exaceae, the most species-rich genus Sebaea has received very little attention in terms of phylogenetic or karyological investigations. As a result, the exact number of species remains vague and the relationships with the other members of the Exaceae poorly understood. In this paper, we provide the first comprehensive phylogeny of the Exaceae including most Sebaea species known so far based on four cpDNA sequence regions. In addition, morphological and karyological characters were mapped on the inferred phylogenetic trees to detect possible non-molecular synapomorphies. Our results reveal the paraphyly of Sebaea and highlight new generic relationships within the Exaceae. Sebaea pusilla (lineage S1--Lagenias) forms a highly supported and early diverging clade with Sebaeas.str. (clade S2 -Sebaea). A third clade of the former Sebaea s.l. (clade S3--Exochaenium) contains exclusively tropical African species, and is sister with a large clade containing all the remaining genera of Exaceae. Within the latter, the proposed sister relationships between the recently described Klackenbergia and Ornichia are highly supported. Optimization of several morphological characters onto the inferred phylogenetic trees reveals several synapomorphies for most highly supported clades. In particular, lineage S1 (Lagenias) is supported by medifixed anthers that are inserted at the base of the corolla tube and cubical seeds with polygonal testa cells; clade S2 (Sebaea) is supported by both the presence of secondary stigmas along the style and ridged seeds with rectangular testa cells arranged in row; clade S3 (Exochaenium) is supported by its particular gynoecium (stylar polymorphism and clavate, papillose stigma). Finally, karyological reconstructions suggest a basal number of x=7 for the Exaceae and several episodes of dysploidy leading to x=8 and 9.

Within the Gentianaceae-Exaceae, the most species-rich genus Sebaea has received very little attention in terms of phylogenetic or karyological investigations. As a result, the exact number of species remains vague and the relationships with the other members of the Exaceae poorly understood. In this paper, we provide the first comprehensive phylogeny of the Exaceae including most Sebaea species known so far based on four cpDNA sequence regions. In addition, morphological and karyological characters were mapped on the inferred phylogenetic trees to detect possible non-molecular synapomorphies. Our results reveal the paraphyly of Sebaea and highlight new generic relationships within the Exaceae. Sebaea pusilla (lineage S1--Lagenias) forms a highly supported and early diverging clade with Sebaeas.str. (clade S2 -Sebaea). A third clade of the former Sebaea s.l. (clade S3--Exochaenium) contains exclusively tropical African species, and is sister with a large clade containing all the remaining genera of Exaceae. Within the latter, the proposed sister relationships between the recently described Klackenbergia and Ornichia are highly supported. Optimization of several morphological characters onto the inferred phylogenetic trees reveals several synapomorphies for most highly supported clades. In particular, lineage S1 (Lagenias) is supported by medifixed anthers that are inserted at the base of the corolla tube and cubical seeds with polygonal testa cells; clade S2 (Sebaea) is supported by both the presence of secondary stigmas along the style and ridged seeds with rectangular testa cells arranged in row; clade S3 (Exochaenium) is supported by its particular gynoecium (stylar polymorphism and clavate, papillose stigma). Finally, karyological reconstructions suggest a basal number of x=7 for the Exaceae and several episodes of dysploidy leading to x=8 and 9.

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14 citations in Scopus®
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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Institute of Systematic Botany and Botanical Gardens
Dewey Decimal Classification:580 Plants (Botany)
Language:English
Date:2009
Deposited On:05 Mar 2010 08:41
Last Modified:05 Apr 2016 13:57
Publisher:Elsevier
ISSN:1055-7903
Publisher DOI:https://doi.org/10.1016/j.ympev.2009.07.025
PubMed ID:19646540
Permanent URL: https://doi.org/10.5167/uzh-31143

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