The Hibbertia polystachya–H. spicata (Dilleniaceae) species group in Western Australia
THIELE, K.R.
Hibbertia spicata F.Muell. and H. polystachya Benth. are widespread in south-western Western Australia, where they are unique in Hibbertia Andrews in having flowers in a cincinnus rather than solitary. The boundary between these two species has been problematic, as they mostly differ in the composition and density of indumentum on their sepals and leaves. Close study has revealed that H. polystachya is widespread and taxonomically relatively straightforward, while H. spicata sens. lat. comprises six distinctive, readily resolvable species (including H. leptotheca (J.R.Wheeler) K.R.Thiele comb. et stat. nov., previously H. spicata subsp. leptotheca J.R.Wheeler) differing in leaf and sepal indumentum, number of flowers in the cincinnus, floral bract shapes, stamen number, and number and arrangement of staminodes. New species described here are H. capensis K.R.Thiele sp. nov., H. asterella K.R.Thiele sp. nov. and H. subglabra K.R.Thiele sp. nov. The new name H. prolata K.R.Thiele is provided for a widespread taxon based on Hemistephus linearis J.Drumm. ex Harv. With these species removed, H. spicata is recircumscribed and is now more restricted in distribution.
