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

Cladistic analyses of Stylidiaceae (Asterales), using Donatiaceae as outgro up and with both morphological and molecular characters, produced two equal ly parsimonious cladograms. The analyses used morphological characters for 26 species and molecular characters from the chloroplast DNA genes rbcL, an d ndhF for 12 species. The cladograms indicate that Levenhookia and Stylidi um are sister groups and that Oreostylidium is nested within Stylidium. The latter result is remarkable because Stylidium has several significant flow er specialisations that Oreostylidium lacks and because Oreostylidium is en demic to New Zealand, where Stylidium is missing. The simple flowers of Ore ostylidium may have evolved by reduction and paedomorphosis of the zygomorp hic and sensitive flowers of a Stylidium-like ancestor, a change caused by adaptation to a new environment lacking a suitable pollinator. In connectio n with a switch to unspecialised pollinators or self-fertilisation, the flo wers of Oreostylidium apparently became fertile at a morphologically immatu re or reduced stage.