Phylogenetic analyses of the Amaryllidaceae based on cpDNA sequences rbcL and trnL-F are not able to adequately resolve the phylogeny of the ostensibly monophyletic neotropical clade of the family due to low levels of base substitution among genera, especially within the Andean tribes Eucharideae and Stenomesseae. We have thus broadly sampled neotropical Amaryllidaceae and generated sequences of the internal transcribed spacer region of 18s-26s nrDNA in the hopes that greater levels of variation would better resolve the relationships of the American genera. Cladistic analyses of our current matrix support the following conclusions with high bootstrap and jackknife values: 1) tribe Stenomesseae as presently conceived is polyphyletic; the petiolate genera of tribe Stenomesseae (Eucrosia, Phaedranassa, Rauhia, Mathieua, petiolate Stenomesson) should be combined with tribe Eucharideae; 2) Eustephieae is distinct from Stenomesseae; 3) Zephyranthes is likely polyphyletic; 4) Rhodophiala is distinct from Hippeastrum, and very likely polyphyletic; 5) the tribe Griffineae (Worsleya and Griffinia) is distinct from Hippeastreae; and 5) tribe Hymenocallideae should be recognized as distinct from Eucharideae.

Key words: Amaryllidaceae, phylogeny, molecular systematics, Neotropics, ITS