Colloquia: Systematic and Evolutionary Perspectives on Apomixis
Hörandl, Elvira .
Geographical parthenogenesis and evolution of apomixis in Ranunculus.
Apomixis, the asexual reproduction via seed, confers short-term evolutionary advantages. Apomictic plants have larger distribution areas than their sexual relatives and colonize more frequently previously glaciated regions. This phenomenon, called “geographical parthenogenesis”, contradicts the general predominance of sexuality and has been controversially referred to various different intrinsic and external factors (Hörandl 2006, New Phytol 171: 223–236). We attempt to elucidate the causality of geographical parthenogenesis by analysis of population genetic structure, breeding systems, fertility, genome size measurements and experimental work on buttercups (Ranunculus). Range fluctuations during periods of climatic oscillations have triggered polyploidization of sexual taxa, thereby increasing frequencies of shifts to apomixis. The establishment of asexual plants is enhanced by multiple factors: (1) apomixis allows for the reproduction via single individuals, which is advantageous for rapid colonizations (Baker’s Law); (2) genetic structure and divergence of sexual and apomictic populations suggest multiple, rapid founder events; (2) selection for stability of cytotypes enhances maintenance of different distributions between sexual and apomictic populations; (3) elevated levels of heterozygosity in apomictic plants may enhance vigor and ecological flexibility; and (4) genetic diversity within apomictic populations is maintained via facultative recombination. We conclude that climatic changes, especially glaciations, have provided short-term opportunities for the origin and establishment of apomixis. Nevertheless, molecular phylogenetic reconstructions suggest that such opportunities have not occurred frequently in the evolution of the genus, which helps to explain the general predominance of sexual reproduction.
The project links molecular ecology, plant evolution, reproductive biology and biogeography. Understanding the evolution of apomictic plants is further releveant for potential applications of apomixis in plant breeding.
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1 - University of Vienna, Institute for Botany, Dept. of Higher Plant Systematics and Evolution, Rennweg 14, Vienna, A-1030, Austria
Presentation Type: Symposium or Colloquium Presentation
Location: 551A/Convention Center
Date: Wednesday, August 4th, 2010
Time: 4:00 PM