Molecular Phylogeny and Character Evolution of Carnivorous Plant Families in Caryophyllales — Revisited

Recent phylogenetic analyses based on single gene and combined data sets have substantially increased our knowledge of the phylogeny of Caryophyllales s.l., indicating that additional carnivorous families are related to this alliance. In earlier contributions towards a reassessment of inter- and infrafamilial relationships slowly evolving genes had been preferred for phylogenetic inference. The resulting tree topologies based on rbcL and 18S rDNA, however, were characterized by limited resolution, low internal support and topological incongruence. Therefore genomic regions evolving more rapidly have been used in subsequent studies. Comparative sequencing of the matK gene and the flanking trnK intron region as well as combined analyses based on plastid matK, atpB, rbcL, and nuclear 18S rDNA have effectively improved resolution and internal support. Tree topologies revealed Caryophyllales s.l. as monophyletic group and indicated a clear division into two sister clades, the "core" and the "non-core" Caryophyllales (with Rhabdodendraceae and Simmondsiaceae with unclear affinities). Contrary to the "core" group (with Asteropeiaceae and Physenaceae as successive sister groups), which corresponds largely to the previous circumscription of the order, the monophyly of "non-core" Caryophyllales comprising Polygonaceae, Plumbaginaceae, Frankeniaceae, and Tamaricaceae along with the carnivorous families Droseraceae, Nepenthaceae, Drosophyllaceae, Dioncophyllaceae, and Ancistrocladaceae are a recent discovery. Based on reliable tree topologies it is hypothesized that pitfall traps of Nepenthes and snap traps typical for Aldrovanda and Dionaea were derived from a common ancestor with adhesive flypaper traps. With exception of Triphyophyllum carnivory was secondarily lost in the remaining Dioncophyllaceae (Dioncophyllum, Habropetalum) and all taxa of Ancistrocladaceae.