Phylogenetic relationships in Saxifragaceae sensu lato: A comparison of topologies based on 18S rDNA and RBCL sequences

Abstract

Relationships among the morphologically diverse members of Saxifragaceae sensu lato were inferred using 130 18S rDNA sequences. Phylogenetic analyses were conducted using representatives of all 17 subfamilies of Saxifragaceae sensu lato, as well as numerus additional taxa traditionally assigned to subclasses Magnoliidae, Caryophyllidae, Hamamelidae, Dilleniidae, Rosidae, and Asteridae. The analysis indicates that Saxifragaceae should be narrowly defined (Saxifragaceae sensu stricto) to consist of - 30 herbaceous genera. Furthermore, Saxifragaceae s. s. are part of a well-supported clade (referred to herein as Saxifragaceae) that also comprises Iteoideae, Pterostemonoideae, Ribesioideae, Penthoroideae, and Tetracarpaeoideae, all traditional subfamilies of Saxifragaceae sensu lato, as well as Crassulaceae and Haloragaceae (both of subclass Rosidae), Paeoniaceae (Dilleniideae), and Hamamelidaceae, Cercidiphyllaceae, and Daphniphyllaceae (all of Hamamelidae). The remaining subfamilies of Saxifragaceae senso lato fall outside this clade. Francoa (Francooideae) and Bauera (Baueroideae) are allied respectively, with the rosid families Greyiaceae and Cunoniaceae, Brexia (Brexioideae), Pamassia (Pamassioideae), and Lepuropetalon (Lepuropetaloideae) appear in a clade with Colastraceae. Representatives of (Phyllomoideae, Eremosynoideae, Hydrangeoideae, Escalloniodeae, Montinioideae, and Vablioideae are related to taxa belonging to an expanded asterid clade (Asteridae sensu lato). The relationships suggested by analysis of 18S rDNA sequences are highly concordant with those suggested by analysis of rbcL sequences. Furthermore, some relationships are also supported in larger part by other lines of evidence, including embryology, serology, and iridoid chemistry.