Tragopogon is a member of subtribe Scorzonerinae of tribe Lactuceae (Asteraceae: Cichorioideae). Mavrodiev et al. (2004) showed Scorzonerinae to be well-supported as monophyletic, comprising in addition to Tragopogon, Epilasia, Podospermum, Koelpinia, Lasiospora, Pterachaenia, Takhtajaniantha, and Geropogon. The sister group of Tragopogon appears to be the small genus Epilasia. The entire clade is primarily centered on eastern Europe and adjacent Asia with a center of distribution in the Mediterranean region. Close relatives of the subtribe that are good outgroups and models with genomic resources are Lactuca and Cichorium.
Tragopogon is a large Eurasian genus of approximately 150-200 species. The genus occurs throughout Eurasia from the U.K. to China and India with a few species in North Africa; most of the diversity of the genus is found in eastern Europe to western Asia. Relationships within Tragopogon remain largely unresolved despite the use ~ 6970 bp (Mavrodiev et al., 2012). Although approximately 150 species names seem valid based on the literature (reviewed in Mavrodiev et al., 2005, 2008a), DNA analyses have revealed morphologically cryptic species (Mavrodiev et al., 2007, 2008a-c). For example, several of the geographically widespread species as long-recognized (T. porrifolius, T. dubius, and T. pratensis) actually comprise a number of distinct species, most of which remain to be named (e.g., Mavrodiev et al., 2007, 2008a, c). Therefore, the total number of species accepted in most comprehensive taxonomic treatments (summarized in Mavrodiev et al., 2007, 2008a-c) is likely an underestimate with the actual number closer to 200.
Bell et al. (2012) estimated that Tragopogon diversified rapidly ~ 2.6 mya ~ (1.41 – 4.2 Mye using various clock estimates). The diversification rate of Tragopogon is approximately 2.0-4.75 species/My, providing another clear example of a rapid Eurasian radiation. These dates coincide with marked climatic and topographic changes in their area of occurrence, the Mediterranean. Other speciose Eurasian lineages occurring in the same dry meadow habitats as Tragopogon also show evidence of rapid radiation at the same time (Bell et al., 2012; Valente et al. 2010).
Significantly, the speed of radiation of Tragopogon species is also close to many other examples of rapid plant radiations from around the world (reviewed in Valente et al., 2010). For example the genus may have radiated even faster than Mediterranean Cistus (speciation rate of 1.46 – 2.44 species/My), alpine Soldanella (1.64 – 2.55 species/My), South American Lupinus (1.30 – 3.78 species/My1), and Neotropical Gentaniella (1.64 – 2.55 species/My)(reviewed in Valente et al., 2010; Bell et al., 2012).
Phylogenetic studies of Tragopogon have also helped resolve relationships of the diploid parents of the two New World polyploids, showing that they are distantly related and in different subclades if this large genus. Tragopogon dubius and T. porrifolius are the most closely related, in the Majores Clade and Hebecarpus clades, respectively; T. pratensis is in the Tragopogon subclade (Mavrodiev et al., 2005, 2012). Furthermore, as noted all three diploids appear to be non-monophyletic adding to the need for more detailed work at the population and species levels.
One of 10,000 shortest trees saved of length 591 resulting from maximum parsimony analyses of the Tragopogon internal and external transcribed spacer data matrix for 52 taxa. Arrows indicate branches that collapse in the strict consensus. Numbers above branches indicate branch lengths. Jackknife/bootstrap values for nodes receiving >50% support are indicated in italics below the branches; T. dubius, T. porrifolius, and T. pratensis are circled. From Mavrodiev et al. (2005; see also 2012).