Nuclear ribosomal DNA (nrDNA) concerted evolution in natural and artificial hybrids of Armeria (Plumbaginaceae)

Abstract

Nuclear ribosomal DNA (nrDNA) internal transcribed spacer (ITS) sequences from artificial hybrids and backcrosses between Armeria villosa ssp. longiaristata and A. colorata were studied to assess the possible effects of concerted evolution in natural hybrids. F1 artificial hybrids show the expected pattern of additive polymorphisms for five of the six variable sites as estimated from direct sequences. However, homogenization of polymorphism is already observed in the F2, and is biased towards A. colorata except for one site. In backcrosses, an expected tendency towards homogenization of polymorphic sites in the direction of the recurrent parent is observed for five sites, although this does not necessarily imply concerted evolution. Conversely, the sixth site appears to elude such a mechanism and thus provides additional support for the occurrence of biased concerted evolution. Our findings are relevant to interpreting phylogeographic patterns involving gene flow and are also consistent with the hypothesis of a hybrid origin of A. villosa ssp. carratracensis.

Evolutionary history of Orinus thoroldii (Poaceae), endemic to the western Qinghai-Tibetan Plateau in China

“…We also calculated the indirect plastid gene flow among populations (N e m) based on the equation N e m ¼ ([1/F ST ] À 1)/2: where, N e was the effective population size of female individuals while m was the migration rate (Freeland et al, 2011). Furthermore, for nrITS sequences, a site was classified as heterozygous if a double peak was found at the same position in both strands and the weakest signal was at least 25% of the strength of the strongest (Fuertes-Aguilar et al, 1999;Fuertes-Aguilar and Nieto-Feliner, 2003). We determined nrITS types using PHASE version 1.0 for heterozygous individuals (Stephens et al, 2011).…”

Molecular evidence for hybridization between invasive Solidago canadensis and native S. virgaurea

“…Although nrDNA genes undergo concerted evolution relatively quickly (e.g., Fuertes Aguilar et al 1999), additive polymorphism pattern detected in the ITS region has been successfully used in the previous studies on interspecific hybridization in many different genera of plants (e.g., Soltis et al 1995;Zalewska-Gałosz and Ronikier 2012;Zalewska-Gałosz et al 2014;Bobrov et al 2015). A lack of any signs of recombination or homogenization between both parental ITS ribotypes may suggest relatively recent forming of hybrid individuals and/or lack of generative propagation.…”

Genetic analysis based on plastidial and ribosomal sequences of the endemic bi-edaphic taxonJurinea pinnata(Lag.) DC. (Compositae) in the Guadix-Baza Basin

“…International Union of Pure and Applied Chemistry (IUPAC) ambiguity codes were used to codify polymorphic positions. Following the recommendations of Fuertes-Aguilar et al (1999a), sites were considered polymorphic (additive polymorphic sites (APSs)). When it was possible, identification of matching ITS ribotypes was inferred by subtraction (Clark 1990).…”

“…nrDNA sequences are useful in the detection of hybridization events (Emshwiller & Doyle 1998;Widmer & Baltisberger 1999). In this case, nucleotide additive patterns, which combine parental ribotypes differentially inherited in the hybrid genome as a result of a recent hybridization event, can emerge (Fuertes-Aguilar et al 1999a;Plume et al 2013). nrDNA sequences have also been used in the study of plants adapted to different types of substrates (Cecchi et al 2011) and ecotypes (Schechter & Bruns 2008).…”