Phylogeny and generic interrelationships of the Stylidiaceae (Asterales), with a possible extreme case of floral paedomorphosis.

Cladistic analyses of Stylidiaceae (Asterales), using Donatiaceae as outgroup and with both morphological and molecular characters, produced two equally parsimonious cladograms. The analyses used morphological characters for 26 species and molecular characters from the chloroplast DNA genes rbcL and ndhF for 12 species. The cladograms indicate that Levenhookia and Stylidium are sister groups and that Ore- ostylidium is nested within Stylidium. The latter result is remarkable because Stylidium has several significant flower specialisations that Oreostylidium lacks and because Oreostylidium is endemic to New Zealand, where Stylidium is missing. The simple flowers of Oreostylidium may have evolved by reduction and paedomorpho- sis of the zygomorphic and sensitive flowers of a Stylidium-like ancestor, a change caused by adaptation to a new environment lacking a suitable pollinator. In connection with a switch to unspecialised pollinators or self-fertilisation, the flowers of Oreostylidium apparently became fertile at a morphologically immature or reduced stage.