Microsatellite evidence for low genetic diversity and reproductive isolation in tetraploidCentaurea seridis(Asteraceae) coexisting with diploidCentaurea asperaand triploid hybrids in contact zones

Abstract

Survival of polyploids in nature depends on several factors, including competition from diploid relatives and increased genetic diversity. Unlike other reported Centaurea polyploid complexes, diploid Centaurea aspera and tetraploid Centaurea seridis coexist in hybrid zones with frequent triploid individuals. The polyploid origin of C. seridis, the genetic diversity and population structure of the three cytotypes, and the degree of genetic differentiation among them were analyzed in seven mixed-ploidy zones, involving different subspecies and ecological conditions. Ploidy was determined by flow cytometry. Microsatellite data suggested an allopolyploid origin of C. seridis. In the contact zones, diploids and tetraploids were genetically differentiated. When compared with the related C. aspera, a low genetic diversity was observed in C. seridis, which is uncommon in tetraploids. Furthermore, although diploid individuals were grouped in a single widespread genetic cluster, tetraploids were grouped in two highly differentiated clusters and showed significant isolation by distance. This genetic pattern in C. seridis may be related to a minimal gene flow with diploid relatives and/or other genetic factors, such as rare polyploidization events, founder effects or an increased selfing rate. Neither taxonomic assignment at subspecies level, nor ecological conditions could explain the genetic differentiation between tetraploid clusters.

The population genetics of the fundamental cytotype-shift in invasive Centaurea stoebe s.l.: genetic diversity, genetic differentiation and small-scale genetic structure differ between cytotypes but not between ranges

“…Most studies on polyploid complexes have revealed higher genetic diversity in polyploids than in diploids (e.g. Eliášová et al 2013 and references therein; but see Ferriol et al 2014). However, we explicitly investigated this difference with a focus on GCTs.…”

A rare case of a natural contact zone in Morocco between an autopolyploid and an allopolyploid of Centaurea aspera with sterile tetraploid hybrids

“…subdecurrens Mateo & Crespo, have been cited. These have been found between northern Castell on and Almer ıa on coastal sand dunes (El Saler, Santa Pola, Guardamar and Calblanque) and on coastal pebble dunes (Marjal dels Moros and Chilches) Ferriol et al 2012Ferriol et al , 2014. In Sax (inland Alicante), C. aspera subsp.…”

“…cruenta also coexist, and hybrid individuals C. x subdecurrens nothosubsp. oblanceolata Merle et al have been observed Ferriol et al 2014).…”

“…Recently, a polyploid complex involving the diploid C. aspera L. and the tetraploid C. seridis L. has been cited in several contact zones located in eastern Spain Ferriol et al 2012Ferriol et al , 2014. Unlike the other reported polyploid complexes in Centaurea, highly sterile triploid hybrids between these two taxa are very frequent in nature.…”

“…Ferriol et al (2012) confirmed that the triploid C. x subdecurrens Pau represents a true F 1 offspring between C. aspera and C. seridis. Genetic analyses have shown that backcrossing events and gene flow are very rare or absent, and that genetic diversity is higher in diploid than in tetraploid individuals (Ferriol et al 2012(Ferriol et al , 2014. Microsatellite markers have also suggested an allopolyploid origin of C. seridis, with C. aspera as one of the parental species.…”