Since the division of the caesalpinioid tribe Cassieae sensu Bentham into five subtribes by Irwin and Barneby, the monophyly of these individual groups has largely gone untested. Of these subtribes, Dialiinae exhibits the greatest generic diversity and is of interest due to its morphological diversity and biogeographic distribution patterns. Dialiinae includes 13 genera and ca. 63 species of trees and is collectively of circumtropical distribution, although individually many of the genera have restricted distributions. Several of these taxa are extremely rare and at least one may now be extinct. Morphological characters of interest not commonly observed in caesalpinioid legumes but present in the Dialiinae include: indehiscent, drupaceous or samaroid fruits, cymose inflorescence structure, reduction in the number of floral organs of one or more whorls from the typical legume flower, basifixed apically dehiscent anthers, and imbricate descending corolla aestivation. A morphological phylogenetic analysis was conducted that incorporated 83 morphological characters and 62 species, including representatives of all genera of Dialiinae, all remaining genera of Cassieae, the genus Poeppigia (Caesalpinieae), and five genera of Cercideae as outgroup taxa. Poeppigia was included to assess whether morphological data support recent molecular results that place the genus within Dialiinae. Our analysis does not support the monophyly of Dialiinae, with one genus of the subtribe isolated from the remaining taxa. In addition, the Australian subtribe Labicheinae and the subtribe Duparquetiinae are nested within Dialiinae. The diversity of floral structure and fruit morphology and the resulting evolutionary and biogeographic implications are discussed in light of the phylogeny obtained.

Key words: biogeography, Leguminosae, phylogeny