Chalcone Synthase Gene Lineage Diversification Confirms Allopolyploid Evolutionary Relationships of European Rostrate Violets

Abstract

Phylogenetic relationships among and within the subsections of the genus Viola are still far from resolved. We present the first organismal phylogeny of predominantly western European species of subsection Rostratae based on the plastid trnS-trnG intron and intergenic spacer and the nuclear low-copy gene chalcone synthase (CHS) sequences. CHS is a key enzyme in the synthesis of flavonoids, which are important for flower pigmentation. Genes encoding for CHS are members of a multigene family. In Viola, 3 different CHS copies are present. CHS gene lineages obtained confirmed earlier hypotheses about reticulate relationships between species of Viola subsection Rostratae based on karyotype data. Comparison of the CHS gene lineage tree and the plastid species phylogeny of Viola reconstructed in this study indicates that the different CHS copies present in Viola are the products of both recent and more ancient duplications.

Inferring Species Networks from Gene Trees in High-Polyploid North American and Hawaiian Violets (Viola, Violaceae)

“…The cosmopolitan genus Viola (Violaceae), with 500–600 species of violets and pansies, comprises numerous hybrid and polyploid complexes in the northern hemisphere (Miyaji 1913; Moore and Harvey 1961; Clausen 1964; Fabijan et al 1987; Ballard et al 1998; Nordal and Jonsell 1998; van den Hof et al 2008; @x Hepenstrick 2009; Marcussen et al, 2011). From a putative base number of x = 6 or x = 7, extant chromosome numbers range from dysploid 2 n = 4 in V. modesta , the lowest number known in angiosperms and also found in five other genera unrelated to Viola and Violaceae, to at least 20-ploid 2 n = ca.…”

“…While the lowest chromosome number of section Chamaemelanium is diploid (2 n = 12), the three sections Melanium (dysploid, 2 n probably between 4 and 16; unpublished data), Plagiostigma (2 n = 24), and Viola (2 n = 20) have been shown to be allotetraploids between diploid species from the lineage of section Chamaemelanium (the CHAM lineage) and another, unidentified diploid lineage (the MELVIO lineage) (Marcussen et al 2011). Secondary polyploidy has occurred internally in all four sections (e.g., Miyaji 1913, Miyaji 1929; Clausen 1964; McPherson and Packer 1974; Fabijan et al 1987; Erben 1996; van den Hof et al 2008; Marcussen et al 2010). …”

Species delimitation in the Ponto-Caucasian Viola sieheana complex, based on evidence from allozymes, morphology, ploidy levels, and crossing experiments

“…The allopolyploid relationships among the species of Viola subsection Rostratae in Europe have been investigated in a series of studies using chromosome cytology (Moore and Harvey 1961), low-copy nuclear gene phylogeny (van den Hof et al 2008), and microsatellite markers (Hepenstrick 2009). Within the Rostratae it is not uncommon that hybrids between polyploids and their lower-ploid progenitors are not completely sterile and that gene flow may happen between the species.…”

“…), which has some 50 species worldwide, but are presumably not monophyletic within this subsection (cf. Harvey 1966;van den Hof et al 2008). Historically, different woodland species have often been united under the collective species names V. canina L., V. sylvestris Lam.…”

Isolation of plant nuclei suitable for flow cytometry from species with extremely mucilaginous compounds: an example in the genus <i>Viola</i> L. (Violaceae)

“…Taxa of these sections are well known for their taxonomic complexity, apparently caused by several factors: (a) scarcity of reliable diagnostic morphological characters; (b) high phenotypic plasticity; (c) frequent interspecific hybridizations; and (d) assumed past reticulate evolution within the section and subsection (Ballard & al., 1999;Yockteng & al., 2003;Van den Hof & al., 2008).…”