Systematics of Arnica, subgenus Austromontana and a new subgenus, Calarnica (Asteraceae : Senecioneae)

Seven species are recognized in Arnica subgenus Austromontana and two species in a new subgenus Calarnica based on a critical review and conservative revision of the species. Chromosome numbers are given for 91 populations representing all species, including the first reports for Arnica nevadensis. Results of apomixis, vegetative reproduction, breeding studies, and artificial hybridizations are given. Interrelationships of insect pollinators, leaf miners, achene feeders, and floret feeders are presented. Arnica cordifolia, the ancestral species consists largely of tetraploid populations, which are either autonomous or pseudogamous apomicts, and to a lesser degree diploid, triploid, pentaploid, and hexaploid populations. It has given rise to Arnica nevadensis which is tetraploid and autonomously apomictic, and to a complex of discoid populations treated here as a single polymorphic species, Arnica discoidea, with both diploid and tetraploid, sexual and pseudogamous apomictic races. Arnica spathulata, derived from Arnica discoidea, is largely restricted to serpentine soils and is a sexual diploid, with a few pseudogamous tetraploid apomictic populations. Arnica latifolia, the most polymorphic species, has arisen from Arnica cordifolia, although it has remained largely sexual and diploid. Arnica latifolia has given rise to Arnica cernua, the serpentine sexual, diploid endemic, and to Arnica gracilis, probably through hybridization with other species. Arnica gracilis now exists largely as a series of autonomously apomictic triploid races. The subgenus Calarnica was possibly derived from subgenus Austromontana by way of Arnica spathulata through Arnica venosa, the latter giving rise to Arnica viscosa. These latter two species are rare sexual diploids.Science, Faculty ofBotany, Department ofGraduat