Toward a resolution of Campanulid phylogeny, with special reference to the placement of Dipsacales

Over the last two decades our understanding of angiosperm phylogeny has improved dramatically. Progress was initially based on large-scale analyses of chloroplast rbcL sequences (e.g., Chase & al., 1993; Savolainen & al., 2000b) but data matrices have more recently included loci from all three genomes (e.g., Zanis & al., 2002; Qiu & al., 2005). In addition, studies based on more targeted samples and/or testing novel genetic markers have generally confirmed the same broad patterns of relationship (e.g., Mathews & Donoghue, 2000). Increasing confidence in major relationships is reflected in the emergence of new classification schemes (e.g., APG II, 2003), sometimes entailing new, or at least newly defined, taxonomic names (e.g., Cantino & al., 2007). However, despite remarkable progress several parts of the broad angiosperm tree have remained poorly resolved and this is hampering evolutionary studies that depend directly upon such phylogenetic knowledge. Here we focus attention on one of these unresolved regions, specifically relationships among the major lineages within what has become known as the euasterid II (e.g., APG, 1998; APG II, 2003) or campanulid clade (Bremer & al., 2002). The “asterid” concept dates back more than 200 years (Wagenitz, 1992). Over time views on the composition and circumscription of the group have varied widely, as have ideas about the relationships of asterids to other angiosperms (cf. Cronquist, 1981; Dahlgren, 1989; Thorne, 1992; Tahktajan, 1997). Our contemporary concept of Asteridae has emerged largely from molecular phylogenetic analyses and is therefore relatively recent (e.g., Chase & al. 1993; APG, 1998). The updated APG II (2003) system recognized ten major asterid lineages—two early branching groups (Cornales, Ericales), and the remaining eight split equally between two large clades, the euasterid I (or Toward a resolution of Campanulid phylogeny, with special reference to the placement of Dipsacales