Phylogenetics of Echinodorus (Alismataceae) based on morphological data

Echinodorus (Alismataceae) is a genus of aquatic and semi-aquatic herbs naturally distributed from Argentina to the USA but commonly used as ornamentals in aquaria worldwide. The phylogeny of the genus was studied on the basis of 96 morphological characters. The analysis resulted in a single most-parsimonious tree supporting a polyphyletic origin of the genus. However, subgenus Echinodorus together with Echinodorus nymphaeifolius formed a clade. Two large clades can be recognized in Echinodorus s.s., but previous subdivisions of the genus are not supported and some earlier proposed subspecific combinations were shown to be non-monophyletic. Addition of continuous characters coded as value ranges enhanced both the resolution and the support values of the tree. Hence, inclusion of continuous overlapping data is encouraged in phylogenetic studies. (c) 2006 The Linnean Society of London, Botanical Journal of the Linnean Society, 2006, 150, 291-305.