Evolution by Reticulation: European Dogroses Originated by Multiple Hybridization Across the Genus Rosa

Abstract

The European dogroses (Rosa sect. Caninae (DC.) Ser.) are characterized by a unique meiosis system ("canina-meiosis"), which controls the heterogamous development of tetraploid egg cells and haploid pollen grains resulting in a pentaploid somatic status. This permanent anorthoploidy is supposed to have originated by a hybridization event in the postglacial period. In this study we present molecular evidence by an analysis of nuclear ribosomal DNA data that dogroses are complex allopolyploids resulting from multiple hybridization events. As previously described, the nrITS-1 region does not undergo concerted evolution in dogroses. Thus, different ITS-1 sequences persist within single individuals. Secondary structure predictions do not point to the existence of pseudogenes within these ITS-1 types. Our data suggest that the pentaploid Caninae genome originated from different members of nondogroses and the now extinct Protocaninae.

Frequent silencing of rDNA loci on the univalent-forming genomes contrasts with their stable expression on the bivalent-forming genomes in polyploid dogroses (Rosa sect. Caninae)

“…Silencing of rRNA genes in univalent, but not bivalent genomes Theoretical predictions based on secondary structure models have suggested that most ITS1 types are potentially functional in dogroses (Ritz et al, 2005). Although the GC content of the g-ITS clade is somewhat lower (55-56%) than that of the b (B59%)-clade, this difference is unlikely to mark the g-clade families as pseudogenes.…”

Phylogeny of Rosa sections Chinenses and Synstylae (Rosaceae) based on chloroplast and nuclear markers

“…Thus, unlike R. sects. Caninae and Rosa (Joly et al, 2006;Ritz et al, 2005), polyploidization does not seem to be an important factor in the evolution of R. sects. Chinenses and Synstylae.…”

“…Hybridization is easy for Rosa species because of overlapping distribution areas and flowering times, common generalist pollinators, and fertile crossbreeds (Jesse et al, 2006;Kevan et al, 1990;Matthews, 1920). Many studies have reported that hybridization has occurred in this genus not only between closely related species but also between species from different sections (Matthews, 1920;Mercure and Bruneau, 2008;Ritz et al, 2005;Schanzer and Kutlunina, 2010;Uggla and Carlson-Nilsson, 2005;Wissemann and Hellwig, 1997). Most species from sections Chinenses and Synstylae are diploid, but polyploidy is very common in other sections especially Caninae and Rosa.…”

“…Many hybridization events have been reported in wild roses (Atienza et al, 2005;Joly et al, 2006;Matthews, 1920;Schanzer and Kutlunina, 2010). The whole section Caninae seems to be of hybrid origin (Fougère-Danezan et al, 2015;Ritz et al, 2005;Wissemann, 1999). Some species of Rosa sects.…”

Morphometric variation and taxonomic identification of thirteen wild rose populations from Tunisia

“…Ser, Banksiae Lindl, Laevigatae Michx. and Bracteatae Thory., each of the four latter sections have only one to three species (RITZ et al 2005). Rehder's system was widely accepted and is still used as a basis for modern treatises (BAILEY 1963, WISSEMAN 2003, NYBOM 2009.…”