THE UTILITY OF PLACENTATION IN THE CIRCUMSCRIPTION OF GENERA OF NEW WORLD LECYTHIDACEAE (BRAZIL NUT FAMILY)

The utility of placentation in the circumscription of ge nera of New World Lecythidaceae (Brazil nut family). The placentation of the 16 known clade s of New World Lecythidaceae and several species of Old World Barringtonia are illustrated and described. The authors conclude that the family possesses axile placentation but an SEM study o f flower development may modify that conclusion. They also restrict the term placenta to all tissue derived from the same carpel to which the ovules are attached. The more basal genera are often defined by placental features as well as by morphological apomorphies and sometimes by molecular data. In contrast, Eschweilera and Lecythis , based on molecular data, are made up of three and five differ ent clades, respectively. Of the three Eschweilera clades, the Eschweilera tetrapetala clade can be separated from the two other clades of the genus by having more than one row of ovules per locule. In contrast, the other two clades of Eschweilera (the E. integrifolia and E. parvifolia clades) posses a single row of ovules in each locule. We conclude that placental data support the segregation of the E. tetrapetala clade as a separate genus while the segregation of the latter two clades is not suppor ted by placental data, even though morphological data support their separation at some taxonomic le vel. Within the currently circumscribed Lecythis , the Lecythis pisonis . and L. corrugata clades are supported by weak placental data; nevertheless, morphological and molecular data support rec ognizing them as distinct genera. The Lecythis ollaria clade, which includes the type species, is supported by mor phological and molecular (100% bootstrap support) data and, if Lecythis were restricted to this clade, the genus would be reduced from 26 to three species. In contrast, the L. poiteaui and L. chartacea clades recovered in this study are not supported by placental or mol ecular data and morphological support