A taxonomic revision of the Stylidium despectum group (Stylidiaceae) from southern Australia

Abstract

A morphological review of the diminutive annual species from the Stylidium despectum R.Br. group (Stylidiaceae) is presented. Twelve species are recognised, of which 10 are endemic in the south-west of Western Australia and two are widespread across southern temperate Australia. Following examination of type material, herbarium collections and field observations, a change of circumscription is presented for S. despectum and S. inundatum R.Br. The former name is applied to a widespread species that occurs in Western Australia, South Australia, Victoria, New South Wales and Tasmania, and is characterised by scattered or rosetted leaves, pink and/or white corolla lobes in a fan-shaped arrangement, and an immobile floral column. S. brachyphyllum Sond. is newly placed into synonymy under S. despectum and a lectotype selected. S. inundatum is redefined as a south-western Australian endemic with scattered leaves, vertically-paired or evenly spreading corolla lobes, and a mobile floral column. A lectotype is designated for S. inundatum, and S. sidjamesii Lowrie & Kenneally is treated as conspecific. S. beaugleholei J.H.Willis is confirmed for Western Australia, South Australia, Victoria and Tasmania. S. asymmetricum Wege, a new and apparently rare species from the Northern Jarrah Forest in south-western Australia, is formally described and revised descriptions are provided for S. longitubum Benth., S. pygmaeum R.Br., S. rhipidium F.L.Erickson & J.H.Willis, S. roseoalatum F.L.Erickson & J.H.Willis, S. roseonanum Carlquist, S. tinkeri Lowrie & Kenneally, S. utricularioides Benth. and S. xanthopis F.L.Erickson & J.H.Willis. A lectotype is designated for S. longitubum Benth. and S. utricularioides var. rosulatum Mildbr. is newly placed into synonymy under S. roseoalatum. A key to species is provided, along with photographs to aid identification. Further field-based studies are required to refine the taxonomy of this group and to better understand the distribution, rarity and conservation status of some of the taxa. In Western Australia, seven species are listed as being of conservation concern, of which S. asymmetricum, S. tinkeri and S. xanthopis require immediate further survey to ascertain whether they should be given Threatened Flora status.