Cladistic analysis of 44 ingroup taxa of New World subtribe Euphorbiinae was undertaken to 1) provide hypotheses about evolutionary relationships, 2) elucidate patterns of character evolution, and 3) reevaluate taxonomic hypotheses and generic segregation of Agaloma, Chamaesyce, Poinsettia and Pedilanthus from Euphorbia. A set of 37 binary and multistate morphological characters were analyzed using maximum parsimony algorithms. Five outgroup taxa from subgn. Esula and genus Cubanthus were used to root the resulting trees. Most parsimonious trees had a consistency index of 0.358 and tree length of 109 steps. The current analyses suggest: (1) the monophyletic origin of New World Euphorbiinae ingroups was not supported strongly; (2) North American Euphorbiinae diverged early from the South American lineage, or they were evolved independently from the different Old World ancestors; (3) subgn. Chamaesyce, Poinsettia and Pedilanthus clades were strongly supported, and they were nested within a paraphyletic subgn. Agaloma (4) the recognition of generic rank for them requires generic segregation for nine groups within subgn. Agaloma, and 5) the secondary woodiness of the major groups in terminal taxa was hypothesized as a result of convergent adaptation to insular or coastal habitats.
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