Circumscription of the Cichorieae

In the traditional circumscription, the Cichorieae were a conveniently recognized tribe, diagnosed by the unique combination of homogamous capitula with 5-dentate, ligulate flowers and the presence of milky latex. Molecular phylogenetic and phylogenomic studies have, however, altered this view. Evidence has been provided that two genera, Gundelia and Warionia, of hitherto uncertain relationships are actually members of the Cichorieae. So far, Gundelia was associated with the Arctotideae (Bremer 1994), Warionia with the Mutisieae or remained unassigned to a tribe (Bremer 1994), or they were treated as the only members of a separate tribe Gundelieae next to Cichorieae (Jeffrey 2006). Both have milky latex but otherwise homogamous capitula with tubular flowers. Hence, by inclusion of these genera the homogamous capitula with 5-dentate, ligulate flowers no longer characterize all the members of the tribe (Kilian & al. 2009).

Neither milky latex nor capitula with only 5-dentate, ligulate flowers represented autapomorphies of the Cichorieae in their traditional sense. Milky latex is otherwise present in some genera of Arctotideae, Cardueae, Liabeae, Mutisieae and Vernonieae (Carlquist 1976), and in a few cases in the Asteroideae (Augier & Mérac 1951; Wagenitz 1976; Bremer 1987, 1994). Milky latex, however, is associated with different anatomical structures in the Compositae. Lactiferous canals, as they are characteristic for all Cichorieae, are otherwise only present in the aerial plant parts of the Arctotideae, whereas other tribes of the Cichorioideae merely have lactiferous cells (Augier & Mérat 1951; Wagenitz 1976). Homogamous capitula with 5-dentate, ligulate flowers are present in a few genera of Mutisieae (Catamixis, Glossarion, Hyaloseris; Bremer 1987, 1994) and, quite evidently by convergent evolution, in the Heliantheae-Coreopsidinae (Fitchia) of subfamily Asteroideae (Carlquist 1957); 5-dentate, ligulate marginal flowers occur in the Vernonieae (Stokesia; Bremer 1987, 1994).

The presence of lactiferous canals in both the subterranean and aerial plant parts seem to be an exclusive feature of the Cichorieae in the present circumscription including Gundelia and Warionia (Augier & Mérac 1951; Wagenitz 1976; Bremer 1987, 1994). Moreover, Gundelia and Warionia share the presence of both (functional) oil ducts and latex canals in the roots (Augier & Mérac 1951) with Scolymus and Scorzonera s.l. (Tieghem 1872; Hoffmann 1890-94; Col 1903-04), while non-functional (relict) oil ducts have been reported from Tragopogon (Tieghem 1885) and Krigia (Holm 1926).

Gundelia, with a much-derived synflorescence of one-flowered capitula aggregated to secondary capitula (syncalathia) of which again a few dozens are aggregated in a second order syncalathium (Classen-Bockhoff & al. 1989), has spiny leaves and pollen similar to Scolymus (Blackmore 1981; Robinson 1994). Gundelia in fact has been shown to form a monophyletic trichotomy with Scolymus and the rest of the Cichorieae by Karis & al. (2001; based on ndhF data). Based on a much broader sampling especially for the basally branching portions of the Cichorieae, Gemeinholzer & al. (in Kilian & al. 2009) and Tremetsberger & al. (2012) have shown that Gundelia forms a clade with Catananche, Hymenonema and Scolymus, which is treated as the subtribe Scolyminae. A phylogenomic study by Mandel & al. (2017) across the Asteraceae confirmed the inclusion of Gundelia in the Cichorieae.

The monospecific Warionia with densely pilose achenes (rare in the Cichorieae but also occurring, e.g., in some species of Scorzonera), has been resolved as sister group to the Cichorieae in their traditional sense in all analyses available so far: Funk & al. (2004), based on trnL-F, ndhF and ITS data, forming a clade together with Gundelia; Goertzen & al. 2003: fig. 3, based on ITS data; Gemeinholzer & al. (in Kilian & al. 2009), based on ITS data; Fu & al. 2016, based on plastid DNA markers. The close relationship to the traditional Cichorieae led Gemeinholzer & Kilian (in Kilian & al. 2009) to establish for Warionia a new subtribe of its own, Warioniinae, within the Cichorieae.

Major clades and recognition of subtribes within the Cichorieae

Whitton & al. (1995) using chloroplast DNA restriction site variation upon 60 Cichorieae taxa were the first to address relationships among major lineages of the tribe and their results agree very well with two more recent attempts by Gemeinholzer & al. (in Kilian & al. 2009), using DNA sequences of the nuclear ITS region and covering 438 taxa, and Tremetsberger & al. (2012), using a subset of 49 species from the former analysis and focusing on divergence time estimations. All analyses revealed similar major lineages.
The analysis by Gemeinholzer & al. (in Kilian & al. 2009) and Tremetsberger & al. (2012) both revealed five major clades, with a total of eleven subclades, within the tribe.

The first three main clades comprise c. 20 % of the species of the tribe (for species proportions here and in the following Hieracium, Pilosella and Taraxacum not considered):

• Clade 1 includes solely Warionia (recognized as the subtribe Warioniinae).
• Clade 2 represents the subtribe Scolyminae.
• Clade 3 represents the subtribe Scorzonerinae

The two main clades 4 and 5 comprise roughly 80 % of the species of the tribe:

• Clade 4 includes five subclades, representing the subtribes Chondrillinae, Crepidinae, Hyoseridinae, Hypochaeridinae and Lactucinae. This main clade comprises 2/3 of the species of the tribe.
• Clade 5 includes three subclades, representing the subtribes Cichoriinae, Hieraciinae and Microseridinae s.l. This main clade comprises somewhat more than 10 % of the species of the tribe.

The backbone of the tree is essentially unresoved and reconstructed differently by Kilian & al. (2009) and Tremetsberger & al. (2012). In the analysis by Kilian & al. (2009) the main clades 4 and 5 group with the Scolyminae clade, whereas the main clades 4 and 5 group with the Scorzonerinaeclade in that by Tremetsberger & al. (2012). The latter topology with the Scolyminae being sister to the Scorzonerinae + clades 4 and 5 is also corroborated by the analyses of chloroplast restriction sites by Whitton & al.(1994), of chloroplast ndhF sequences by Karis & al. (2001) and by the phylogenomic study by Mandel & al. (2017).

Age of the Cichorieae

The estimated minimum age for the most recent common ancestor of the Cichorieae was revealed as c. 26 (23.2-30.3) mya, indicating that the tribe originated no later than Oligocene, and from the inferred N African-Mediterranean ancestral area of Cichorieae (including Gundelieae, Funk & al. 2005), N Africa seems the most plausible region of origin (Tremetsberger & al. 2012). The clades 4 and 5 diversified no later than Middle/Late Miocene or Early Pliocene (c. 21 (16.8-24.4) mya) (Tremetsberger & al. 2012).
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