Systematics Section / ASPT
Paun, Ovidiu , Hörandl, Elvira , Greilhuber, Johann , Stuessy, Tod F. .
Hybridization as the origin of apomixis for a hexaploid population within sexual diploid Ranunculus carpaticola.
Apomixis in different plant groups might have originated through different evolutionary mechanisms. Diploid R. carpaticola is sexual and occurs in Central Slovakia and the Carpathians. Previous morphological and isozyme data have suggested apomictic reproduction and hybrid origin of one hexaploid population of this species from northern Slovakia, involving hybridization with sexual tetraploids of R. cassubicifolius from the northern pre-Alps of Austria. Amplified Fragment Length Polymorphism (AFLP) and microsatellites (SSR) have been used to investigate the genetic and reproductive structure and relationships of nine populations (250 individuals) from the different ploidy levels and species. All diploid and tetraploid populations show high levels of genetic variation, suggesting outcrossing. From the 28 individuals sampled for the hexaploid population of R. carpaticola, 17 individuals represent two very similar clones; the remaining individuals have unique genotypes. Nevertheless, a Character Incompatibility Analysis indicates that the percentage of sexual reproduction in this population is low and comparable to other agamospecies (e.g., R. variabilis). A Principal Coordinate Analysis of the hexaploid population reveals its approximately intermediate position between representatives of the putative diploid and tetraploid parents, which supports a hypothesis of hybrid origin. The somewhat isolated position of the apomictic hexaploid population in factor space, however, suggests that it may have originated from slightly different ancestors (e.g., involving also other microspecies) or that it diverged subsequent to its origin (perhaps involving recombination between parental genomes). Hybridization seems to have caused apomixis, which, in turn, has permitted perpetuation of the hybridogeneous genotypes. The considerable geographic distance of the hybrid population from the putative tetraploid parent, R. cassubicifolius, plus the divergent AFLP data between the clones of the hexaploid hybrid population, suggest an ancient hybridization event.
1 - University of Vienna, Institute for Botany, Dept. of Higher Plant Systematics and Evolution, Rennweg 14, Vienna, A-1030, Austria
Presentation Type: Paper
Location: Cottonwood A (Snowbird Center)
Date: Wednesday, August 4th, 2004
Time: 5:15 PM