Temporal frames of 45S rDNA site ‐number variation in diploid plant lineages: lessons from the rock rose genus Cistus (Cistaceae)

The perception that the turnover of 45S rDNA site number in plants is highly dynamic pervades the literature on rDNA evolution. However, most reported evidences come from the study of polyploid systems and from crop species subjected to intense agronomic selection. In sharp contrast with polyploids, the evolutionary patterns of rDNA loci number in predominantly diploid lineages have received less attention. Most studies on rDNA loci changes lack explicit temporal frames, and hence their dynamics could not be assessed. Here, we assess the temporal patterns of rDNA site evolution in Cistus, an entirely diploid lineage. We assessed the number and chromosomal position of 45S rDNA loci in Cistus species using fluorescence in situ hybridization (FISH) and Ag‐nucleolus organizing regions (Ag‐NOR) staining. Maximum likelihood and maximum parsimony reconstructions of the ancestral state of the 45S rDNA locus number were inferred onto a dated phylogeny. 45S rDNA locus number in Cistus ranged from one to four. Maximum likelihood and maximum parsimony reconstructions suggested that the two‐loci state was the ancestral condition in Cistaceae, including the sister genera Tuberaria and Cistus. The most likely basal number of rDNA loci (two) has been maintained from the hypothesized ancient splitting events between Fumana and the remaining Cistaceae lineages in the Oligocene to most of the recent clades of Cistus diversified in the Middle Pleistocene. Our results support the view that...

Source: Biological Journal of the Linnean Society - October 31, 2016 Category: Research Authors: Chiara Totta, Marcela Rosato, Pablo Ferrer ‐Gallego, Fernando Lucchese, Josep A. Rosselló Tags: Research Article Source Type: research