Phylogeny and Classification of the Haemodoraceae

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Abstract
A phylogenetic analysis of the monocot family Haemodoraceae is presented to assess the classification and interrelationships of tribes, genera, and species complexes and to determine patterns of evolutionary and biogeographic change. Evidence is reviewed for the monophylesis of the family (as here delimited) and of some family genera. In order to assign character polarities, two families, Philydraceae and Pontederiaceae, were hypothesized as closest outgroups based on presumed synapomorphies shared with the Haemodoraceae, including: (1) unifacial leaves (Philydraceae) and (2) verrucate pollen wall sculpturing and non-tectate-columellate exine structure (Pontederiaceae). A detailed analysis of the selection, definition, and coding of characters and character states is presented. Computer parsimony algorithms were used to construct most parsimonious trees. Utilizing all characters, including several for which polarity could not be determined, two equally most parsimonious cladograms were derived, differing only in the relative placement of the genera Dilatris and Lachnanthes. A cladistic analysis restricted to only those characters for which polarity could be determined yielded the same two equally parsimonious topologies; one in which correlated characters were scaled yielded one of the two topologies. Cladistic analyses support the monophylesis of the (herein defined) tribes Haemodoreae and Conostylideae. However, of the fourteen genera in the family, Wachendorfia, Haemodorum, and Xiphidium could not be a priori established as monophyletic, and the genera Anigozanthos and Conostylis are paraphyletic. Evolutionary events, as portrayed in the cladograms, are reviewed with emphasis on evolution of trichome anatomy, ovary position, ovule morphology, seed morphology, and chromosome number. Possible biogeographic scenarios support a Gondwanan origin for the Haemodoraceae with one major vicariance event occurring by the continental separation of present Antarctica from South America-Africa. With regard to interfamilial relationships, the Haemodoraceae are hypothesized as the sister group of the family Pontederiaceae, with both families more distantly related to the Philydraceae. Relationships to the Typhales, Bromeliaceae, and Zingiberales are still ambiguous, but the possibility of a close relationship of the Haemodoraceae-Pontederiaceae to the Zingiberales is considered.