Discussion of Phylogenetic Relationships
The phylogenetic tree shown on this and subsequent pages is drawn after that reported in Panero and Funk (2008) based on analyses of combined sequence data from multiple chloroplast loci including the genes matK, ndhD, ndhI, ndhF, rbcL, rpoB, exon1 of rpoC1, and the intron and intergenic spacer regions of the trnL-trnF. Each of the major clades of Asteraceae (subfamilial and tribal clades) was inferred in both Maximum Parsimony and Bayesian phylogenetic analyses with significant measures of clade support (bootstrap and posterior probability respectively). Relationships among these clades were also resolved with significant statistical support and were robust to method with the exception of the relationships of Stifftioideae and Wunderlichioideae. The phylogeny of Panero and Funk (2008) represents the best resolved and statistically supported hypothesis of evolutionary relationships among the major clades of the family currently available. Preliminary results from their study (Panero and Funk, 2008) have been used previously as the backbone phylogeny for the construction of a metatree of the family (Funk et al., 2009). The nomenclature used here is consistent with that of NCBI Genbank.
Relationships among the deepest branches of the Asteraceae tree of life have primarily been elucidated through investigations of the chloroplast genome. Comparative nucleotide studies (Kim and Jansen, 1995, Bayer and Starr, 1998, Panero and Funk, 2008) confirmed the original discovery based on restriction fragment polymorphisms (RFLPs) that Barnadesioideae, lacking the 22 kb inversion present in all other sunflowers (Jansen and Palmer, 1987), is sister to all other Asteraceae. A Cichorioideae clade sister to Asteroideae was recovered with weak bootstrap support in the ndhF study of Kim and Jansen (1995) and identified with strong support (bootstrap and posterior probability) in the multi-locus chloroplast study of Panero and Funk (2008). The multi-locus study also recovered strong statistical support for the Mutisioideae, Stifftioideae, Gochnatioideae, Hecastocleidoideae, Carduoideae, Pertyoideae, Gymnarrhenoideae, and Corymbioideae clades. All family-wide molecular phylogenetic studies to date (Kim and Jansen, 1995, Bayer and Starr, 1998, Kim et al., 2005, Panero and Funk, 2008) have shown support for a monophyletic Asteroideae.
Evidence from the nuclear genetic compartment, an analysis of the nuclear ribosomal internal transcribed spacer (nrITS) region (Goertzen et al., 2003), is congruent with chloroplast results in the relationships of Barnadesioideae and Mutisioideae to other Asteraceae, in the monophyly of the Asteroideae, and in the sister relationship of Athroismeae and Heliantheae s.l. Relationships of other major clades of Asteraceae recovered from the nrITS study (strict consensus tree) are not congruent with chloroplast results. However, these may conservatively be viewed as equivocal because of low statistical support (bootstrap proportions).
The phylogenetic tree presented here primarily reflects the evolutionary history of the chloroplast genome. Asteraceae provide some of the best documented examples of hybrid evolution in plants (Rieseberg et al., 2003, Soltis et al. 2008, Timme et al., 2007), but the full extent of reticulation in the evolutionary history of sunflowers is not yet known, nor how closely this genome phylogeny corresponds to the organismal phylogeny of sunflowers.
No one has provided updates yet.