FISH mapping of 35S and 5S rRNA genes inArtemisiasubgenusDracunculus(Asteraceae): changes in number of loci during polyploid evolution and their systematic implications

Abstract

Fluorescence in situ hybridization (FISH) with 35S and 5S rDNA probes was used to characterize cytogenetically representatives of Artemisia subgenus Dracunculus and allied species and to explore their evolution following polyploidization. At the diploid level two rDNA loci were observed in most species belonging to the A. dracunculus complex, a pattern considered to be the ancestral state for diploid Artemisia. In contrast, representative species from the Eurasian grade which belong to the other major lineage of the subgenus had more heterogeneous rDNA profiles, with three to five loci at the diploid level. Divergent patterns of locus evolution were also detected in polyploids, with the number and distribution of rDNA loci broadly fitting the two main diversification lineages in the subgenus. In the polyploid complex of A. dracunculus, the number of rDNA loci was almost proportional to ploidy, although monoploid genome size was shown to decrease with increasing ploidy. However, in polyploids from the Eurasian grade we found a remarkable reduction in the number of rDNA sites, suggesting that these species might have experienced either a complete loss of loci or a significant reduction in the number of repeats following polyploid formation. © 2013 The Linnean Society of London,

Cytogenetic insights into an oceanic island radiation: The dramatic evolution of pre‐existing traits in Cheirolophus (Asteraceae: Cardueae: Centaureinae)

“…Cheirolophus is also unusual in that the number of 35S rDNA loci is negatively correlated with GS, a situation that contrasts with the widely documented positive associa tion between these traits across angiosperms. Certainly among closely related taxa, GS and 35S loci number are typically seen to increase proportionally with ploidy level (e.g., Pellicer & al., 2010Pellicer & al., , 2013, and while this positive relationship is less strong when considering angiosperms as a whole (Fig. 3D) it is still clearly evident (e.g., Prokopowich & al., 2003).…”

Chromosome evolution in the cosmopolitan genus Lycium (Solanaceae)

“…In Lycium , there are always two signals in diploids, whereas polyploids have a proportionally higher number (Blanco & al., ; Table , Fig. ); thus, this gain is associated with polyploidy events (Hasterok & al., ; Pellicer & al., ).…”

Intergeneric and interspecific hybridizations among <i>Glebionis coronaria</i>, <i>G. segetum</i> and <i>Leucanthemum vulgare</i>

“…The Asteraceae is evolutionally the most advanced family in the plant kingdom and has the largest tribe Anthemideae, so-called Chrysanthemum sensu lato (Kondo et al 2010) that were considered to be evolved during the glacial epoch (Bremer and Humphries 1993;Kondo et al 2003Kondo et al , 2009Pellicer et al 2013Pellicer et al , 2014. Most of the generic members of the Anthemideae have the basic chromosome numbers of X=9 and moreover, they have diploid chromosome number of 2n=18 up to didiploid chromosome number of 2n=198 (Tahara 1915;Dowrick 1952) that seem to be very rare case in the higher plants.…”