Phylogeny and evolution of the Arctium‐Cousinia complex (Compositae, Cardueae‐Carduinae)

Abstract

These authors contributed equally to this publicationThe phylogeny and evolution of the Arctium-Cousinia complex, including Arctium, Cousinia as one of the largest genera of Asteraceae, Hypacanthium and Schmalhausenia, is investigated. This group of genera has its highest diversity in the Irano-Turanian region and the mountains of Central Asia. We generated ITS and rpS4-trnT-trnL sequences for altogether 138 species, including 129 (of ca. 600) species of Cousinia. As found in previous analyses, Cousinia is not monophyletic. Instead, Cousinia subgg. Cynaroides and Hypacanthodes with together ca. 30 species are more closely related to Arctium, Hypacanthium and Schmalhausenia (Arctioid clade) than to subg. Cousinia (Cousinioid clade). The Arctioid and Cousiniod clades are also supported by pollen morphology and chromosome number as reported earlier. In the Arctioid clade, the distribution of morphological characters important for generic delimitation, mainly leaf shape and armature and morphology of involucral bracts, are highly incongruent with phylogenetic relationships as implied by the molecular data. No taxonomic solution for this conflict can be offered, and the characters named are interpreted as homoplasious. Although phylogenetic resolution in the Cousinioid clade is poor, our ITS and rpS4-trnT-trnL sequences contain some phylogenetic information. For example, the six annual species of the Cousinioid clade fall into two groups. Poor phylogenetic resolution probably results from lack of characters and the high number of taxa in this species-rich and comparatively young (ca. 8.7 mya) lineage. We hypothesize that speciation in the Cousinioid clade was mainly allopatric.

A comprehensive generic‐level phylogeny of the sunflower family: Implications for the systematics of Chinese Asteraceae

“…Within Carduinae, the close relationship of Shangwua and Xeranthemum was supported by our analysis and recent studies (Wang et al, ; Wang et al, ). The close relationships of Cousinia + ( Arctium + Schmalhausenia ) and Aucklandia + Frolovia , previously inferred by López‐Vinyallonga et al () and Wang et al (), separately, were also supported in our phylogenetic inferences (PP > 0.95; Fig. B).…”

Chromosome Numbers in the Genera Cousinia, Olgaea and Syreitschikovia (Compositae)

“…However, the complete absence of polyploid chromosome numbers among the 149 species analyzed of the Arctium-Cousinia complex (Watanabe 2002) implies that (allo-)polyploid speciation did not play a role in the evolution of this complex (López-Vinyallonga et al 2009). …”

“…We have found little correspondence between phylogeny and karyology by mapping the chromosome number data for the 63 species present in the Bayesian phylogenetic tree by López-Vinyallonga et al (2009) for which chromosome numbers have been reported (Fig. 3).…”

“…On the basis of our results and the above cited previous works, somatic chromosome numbers in the Cousinioid lineage are 2n=26, 24, 22, 20 and 18 in a dysploid series ranging from x=13 to 9. Previous molecular studies have not clarified whether dysploidy is ascending or descending in the Cousinioid group (López-Vinyallonga et al 2009), but descending dysploidy predominates in other groups of the Cardueae (see Introduction). In the subtribe Centaureinae, basal groups have chromosome numbers ranging from x=16 to 13, whereas the complex of genera with derived features have x=12 to 7 (Garcia-Jacas et al 2001).…”

“…The species of the Arctioid group, which do not exhibit dysploidy, are found in mesophylous mountain areas. Instead, the Cousinioid species, where a dysploid series is found, grow mainly in arid zones (López-Vinyallonga et al 2009). …”