Phylogenetic relationships of Polemoniaceae inferred from 18S ribosomal DNA sequences

Cladistic analyses of chloroplast DNA disagree with current classifications by placing Polemoniaceae near sympetalous families with two staminal whorls, including Fouquieriaceae and Diapensiaceae, rather than near sympetalous families with a single staminal whorl, such as Hydrophyllaceae and Convolvulaceae, To explore further the affinities of Polemoniaceae, we sequenced 18S ribosomal DNA for eight genera of Polemoniaceae and 31 families representing a broadly defined Asteridae. The distribution of variation in these sequences suggest some sites are hypervariable and multiple hits at these sites have obscured much of the hierarchical structure present in the data. Nevertheless, parsimony, least-squares minimum evolution, and maximum likelihood methods all support a monophyletic Polemoniaceae that is placed near Fouquieriaceae, Diapensiaceae and related "ericalean" families.