A revision of Cassinia (Asteraceae: Gnaphalieae) in Australia. 6. Section Cassinia

Abstract

The present paper completes a taxonomic revision of Cassinia subg. Cassinia, a group of 35 species separated from subg. Achromolaena by the structure of its inflorescence (capitula arrangement approximately dichasial, giving rise to flat- or round-topped compound inflorescences, as opposed to the irregular or alternate arrangement of capitula in subg. Achromolaena, where the overall shape of the inflorescence is conical or elongate). The seven species of Cassinia sect. Cassinia (C. aculeata, C. thinicola, C. wilsoniae, C. longifolia, C. aureonitens, C. trinerva and C. cinerea) are keyed, described and illustrated, with discussion of ecology, distribution and variation. Cassinia aculeata subsp. nova-anglica Orchard, C. thinicola Orchard, C. wilsoniae Orchard and C. cinerea Orchard are described as new. Cassinia aculeata is a variable and widespread species. Four morphological variants are described and discussed, although not formally named. Previously suggested hybridisation between C. aculeata and Ozothamnus obcordatus is discussed, and dismissed. A new subspecies, narrowly endemic to the New England region of New South Wales (NSW), and separated by 350 km from subsp. aculeata, is described. Cassinia longifolia is similarly widespread and variable, particularly in indumentum and leaf shape. Again, four more or less distinct local morphological variants are described, but they are not formally named because of problems with satisfactory circumscription. Cassinia thinicola is newly segregated from C. aculeata. It is a strikingly distinct species, confined to coastal habitats north and south of Newcastle, distinguished by its (usually) lack of hairs on the upper leaf surface, ochre-coloured inflorescences and compact habit. Cassinia wilsoniae, confined to Wyperfeld National Park in western Victoria, has hitherto been largely overlooked, with specimens assigned to a broadly circumscribed ‘C. uncata’, or C. aculeata or C. longifolia. It is geographically widely separated from all of these taxa. It is unusual in the genus, in being confined largely to the summits of consolidated sand dunes. It has rather small inflorescences with few capitula, and these are ochre-coloured. The leaf margins are strongly revolute, almost completely covering the midrib below, unlike related taxa where the midrib remains uncovered. Cassinia cinerea is a rare species confined to south-eastern Queensland, and hitherto confused with C. laevis and C. collina, both in subg. Achromolaena (and thus with conical inflorescences). It also differs from both in a range of indumentum and leaf characters. The remaining, previously recognised, species are redescribed in detail, and their nomenclature, variation, ecology and distribution are discussed as required.