Evolution and Phylogeny of the Araceae

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Abstract
The Araceae are exceptionally diverse by nearly all phenetic criteria. The two most widely accepted infrafamilial classification systems, those of Engler and Hutchinson, emphasize vegetative and floral morphology, respectively, and are thus rather dissimilar. A more balanced scheme, in which all available phenetic data are considered, is attempted here. Character state polarities are inferred, and synapomorphies utilized to circumscribe infrafamilial taxa. Among the character states considered primitive for Araceae are: a rhizomatous or caulescent growth habit; simple, cordate leaf blades; parallel venation; a simple, green spathe; bisexual, perigoniate flowers; trilocular ovaries with axile placentation; anatropous, crassinucellate ovules; elongate stamens with longitudinal anther dehiscence; a base chromosome number of x = 7 or 14; and monosulcate, reticulate, binucleate pollen grains lacking starch. These and other conclusions have been employed in a character analysis of araceous subtaxa accepted a priori as natural. Significant features of the classification derived from a cladogram reflecting this analysis include: the merger of Engler''s subfamilies Pothoideae and Monsteroideae, and the dissolution of his Calloideae; a drastic internal rearrangement of the Colocasioideae; and the recharacterization of the Aroideae, involving the transfer of several tribes to the Philodendroideae and the assimilation of the subfamily Pistioideae (Pistia stratiotes L.) and the tribe Thomsonieae (formerly included in subfamily Lasioideae). The following suprageneric nomenclatural novelties are created: CERCESTIDEAE Grayum, trib. nov.; Protarinae (Engl.) Grayum, stat. nov.; REMUSATIINAE Grayum, subtrib. nov.; JASARINAE Grayum, subtrib. nov.; and SCAPHISPATHINAE Grayum, subtrib. nov.