Molecular phylogenetics and patterns of floral evolution in the Ericales

The diverse and species-rich order Ericales has found considerable interest among systematists in recent years. Molecular phylogenetic studies not only have convincingly demonstrated the monophyly of the order, comprising 23 families formerly placed in three different subclasses (Asteridae, Dilleniidae, and Rosidae), but have also resolved Ericales as sister to euasterids. Most ericalean families are well circumscribed and have been or are currently subject to intrafamilial phylogenetic studies. In spite of all the attention that Ericales have received recently, there remains a major challenge, the still largely unresolved deeper nodes in the ericalean phylogeny. This study aims to improve our current knowledge of the interfamilial relationships by expanding on gene and taxon sampling and to evaluate the evolution of important floral characters in light of the resulting phylogeny. We add a nuclear region (26s rDNA) to already published data sets (nuclear: 18s rDNA; mitochondrial: atp1, matR; chloroplast: atpB, ndhF, rbcL, matK, the rps16 intron, the trnT-trnF spacer, and the trnV-atpE spacer), for a total of 11 molecular markers that include nearly 20 kb of sequences. Our analyses, applying both maximum parsimony and Bayesian inference, resolve some of the deeper nodes in the phylogeny. Strongly supported groups, previously unrecognized or only weakly supported, include ( 1) a clade comprising all families except Balsaminaceae, Tetrameristaceae, Marcgraviaceae, Fouquieriaceae, Polemoniaceae, and Lecythidaceae; ( 2) a clade with Sapotaceae, Ebenaceae, and the primuloid families; ( 3) a clade with Symplocaceae, Styracaceae, and Diapensiaceae; and ( 4) a clade comprising the latter three families plus Theaceae, Roridulaceae, Actinidiaceae, Sarraceniaceae, Clethraceae, Cyrillaceae, and Ericaceae. At an analytical level, our results indicate that more data in the form of additional markers do improve resolution and branch support and should eventually lead to a fully resolved ericalean phylogeny. At the level of floral evolution, we demonstrate that sympetaly is a homoplasious character in the order, that a diplostemonous floral ground plan likely arose from haplostemonous flowers in Ericales, and that the combination of ovules with a single integument and cellular endosperm formation is characteristic for two of the major clades in the order.