Abstract
Historical demographic processes and mating systems are believed to be major factors in the shaping of the intraspecies genetic diversity of plants. Among Caryophyllales, the Beta section of the genus Beta, within the Amaranthaceae/Chenopodiaceae alliance, is an interesting study model with species and subspecies (Beta macrocarpa, Beta patula, Beta vulgaris maritima and B.v. adanensis) differing in geographical distribution and mating system. In addition, one of the species, B. macrocarpa, mainly diploid, varies in its level of ploidy with a tetraploid cytotype described in the Canary Islands and in Portugal. In this study, we analyzed the nucleotide diversity of chloroplastic and nuclear sequences on a representative sampling of species and subspecies of the Beta section (except B. patula). Our objectives were (1) to assess their genetic relationships through phylogenetic and multivariate analyses, (2) relate their genetic diversity to their mating system, and (3) reconsider the ploidy status and the origin of the Canarian Beta macrocarpa.
Highlights
The nature of forces that shape genetic diversity of species is a long- standing question in evolutionary biology (Leffler et al, 2012)
The concatenated chloroplastic sequences from the 57 samples of the Beta section and 3 samples from the Corollinae section enabled us to TOUZET et al (b) generate a rooted phylogenetic tree that revealed (Figure 2a) several clades with low bootstrap (BP) and posterior probabilities (PP): (1) a clade composed of all Beta macrocarpa samples except two samples from the Canary Islands, (2) a large clade within which we found most of the B.v. adanensis samples and some Eastern B. v. maritima samples as well as the two B. macrocarpa samples from the Canary Islands, and (iii) a large clade composed mainly of Western B. v. maritima samples
The three nuclear loci sequenced on the same samples led to a nuclear consensus phylogenetic tree (Figure 2b) on which we found this time with a good phylogenetic support: (1) a clear distinct B. macrocarpa clade (BP = 93, PP = 1.00) and (2) a large clade composed of B. v. maritima and B. v. adanensis (BP = 93, PP = 1.00)
Summary
The nature of forces that shape genetic diversity of species is a long- standing question in evolutionary biology (Leffler et al, 2012). Beta (see Biancardi, Panella, & Lewellen, 2012 for the recent evolution of Beta taxonomy) This last section is composed of B. macrocarpa, B. patula and the species complex B. vulgaris, within which can be found wild forms In the present study, we analyze the nucleotide diversity of a representative sampling of species and subspecies of the Beta section (except B. patula) at chloroplastic and nuclear loci in order to: (1) assess their genetic relationships through phylogenetic and multivariate analyses, (2) relate species/ subspecies diversity of the section to their mating system, and (3) reconsider the ploidy status and the origin of the Canarian Beta macrocarpa
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