Marcgraviaceae comprises seven genera and approximately 130 species distributed from southern Mexico to northern Bolivia including the Caribbean islands. Distinctive morphological features include hemiepiphytic habit, hypophyllous glands, reversible heteroblasty, and highly modified bracts which are transformed into pitcher-like extrafloral nectaries. Phylogenetic analysis of rbcL sequence data strongly supports the monophyly of the family and an alliance with Tetrameristaceae, Pellicieraceae, and Balsaminaceae. A possible sister-group relationship of Marcgraviaceae with Tetrameristaceae + Pellicieraceae is weakly supported by this analysis. Marcgraviaceae exhibit an unusually low amount of sequence divergence in comparison to their close relatives. Relationships within the family are investigated using trnL-F and ndhF sequence comparisons. These data resolve two major lineages within Marcgraviaceae corresponding to subfamilies Marcgravioideae and Noranteoideae. The monogeneric Marcgravioideae are united by several morphological synapomorphies and a 4 bp indel in the trnL intron. In contrast, subfamily Noranteoideae appears to be delimited by plesiomorphic morphological characters, but it is supported by molecular data. Despite considerable morphological heterogeneity within Noranteoideae, our sequence data do not resolve currently recognized genera as monophyletic groups.

Key words: Marcgraviaceae, molecular systematics, morphological evolution, phylogeny