| Titre : |
The significance of apomixis in the evolution of the angiosperms: a reappraisal |
| Type de document : |
Extrait d'ouvrage |
| Auteurs : |
Peter van Dijk ; Kitty Vijverberg |
| Année de publication : |
2005 |
| Catégories : |
[CBNPMP-Thématique] Angiospermes
|
| Mots-clés : |
Arnica montana L., 1753 |
| Résumé : |
Apomixis, the ability to produce asexual seeds, constitutes, along with out- crossing and selfing, one of the three major breeding systems in the angiosperms. However, apomixis is by far the least common of these three, despite theoretical advantages of apomixis over outcrossing and selfing. Darlington and Stebbins argued more than 50 years ago that no completely apomictic (sub)genera exist within the angiosperms. Clones lack genetic variation and therefore the ability to adapt to changing environments. In addition it has been suggested that clones degenerate because of the accu- mulation of deleterious mutations. The commonly held view is therefore that apomicts are evolutionary dead ends, doomed to early extinction. Recent genetic studies provide insight in the genetic architecture of apomixis. Apomixis appears to be a genetically complex trait and may therefore be difficult to evolve. Recent progress in angiosperm phylogeny allows for the optimisation mapping of apomixis onto phylogenetic trees. Assuming that aposporous and diplosporous apomixis are non-homolo- gous, the results indicate that gametophytic apomixis arose many times in the history of the angiosperms. Gametophyic apomixis is especially com- mon in the Poaceae, the Asteraceae and the Rosaceae and its phylogenetic distribution is illustrated here within the former two. In both families apomixis is clustered at the (sub)tribal level, i.e., above the genus level. It is argued that some clades may be preadapted in such a way that apomixis evolves more easily, leading to parallel/convergent evolution of the trait. In addition, it now becomes clear that genes that encode for apomixis can be transmitted through pollen in hermaphrodites. In this way apomixis-genes can escape from early extinction and survive for longer periods of evolu- tionary time. The clustering of apomixis at the (sub)tribal level could then be due to a common ancestry or introgression of such apomixis-genes. |
| Lien pérenne : |
DOI : 10.13140/2.1.4567.9042  |
| Permalink : |
https://biblio.cbnpmp.fr/index.php?lvl=notice_display&id=148038 |
Dijk, Peter van, Vijverberg, Kitty
2005
The significance of apomixis in the evolution of the angiosperms: a reappraisal.
In: Plant species-level systematics. A.R.G. Gantner Verl., Ruggell.
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The significance of apomixis in the evolution of the angiosperms: a reappraisal (2005)
