CIRCUMSCRIPTION AND PHYLOGENY OF THE CAMPANULALES

Systematic relationships of the Campanulales were reexamined through the integration of data accumulated from morphological, anatomical, embryological, palynological, cytological, ultrastructural, chemical, molecular, and paleontological studies. Interpretation of these data suggests that the most natural circumscription of the order may be achieved by retaining Asteraceae and Calyceraceae, adding Menyanthaceae, removing Donatiaceae and Stylidiaceae to Ericales, and including Brunonia in Goodeniaceae rather than its own family. Phylogenies based on chloroplast DNA restriction fragment analysis and rbcL sequencing, supported by embryological and chemical data, suggest a basal dichotomy into two clades. The first (Menyanthaceae, Goodeniaceae, Calyceraceae, and Asteraceae) has multinucleate tapetal cells, lacks endosperm haustoria, and produces deterrent chemicals (either seco-iridoids or sesquiterpene lactones, but not both) via the mevalonate pathway. The second (Campanulaceae, Cyphiaceae, Lobeliaceae, Sphenocleaceae, and Pentaphragmataceae) has binucleate tapetal cells and terminal endosperm haustoria, but cannot synthesize deterrent chemicals via the mevalonate pathway. Numerous characteristic morphological features (e.g., epigyny, zygomorphy, secondary pollen presentation, uniovulate ovaries) appear to have had multiple origins within the order, vitiating their use 'as synapomorphies. The order originated no later than the Oligocene, very near the base of the Asteridae, probably in the Cornales-Saxifragales complex.