THE CYTOEVOLUTION OF THE AUSTRALIAN PAPILIONACEAE Valerie E. Sands* (Plate XVI) [Accepted for publication 23rd October 1974] Synopsis Evolutionary development in the Australian Papilionaceae is analysed with special reference to the tribe Podalyrieae, through an integration of data on chromosome numbers, inflorescence morphology and geographic distribution. Chromosome determinations are reported for 242 species of 22 genera in the Podalyrieae, together with 51 species of 13 genera from other tribes. The Podalyrieae is here divided into three groups on chromosome number and inflorescence morphology and the evolutionary pattern of each group has been analysed. Base chromosome numbers of 7, 8 and 9 in the Podalyrieae originated prior to the development of the genera, which appear to have achieved pan-Australian distribution before mid-Miocene isolation of east and west. Only PuUenaea and Dilhcynia developed strongly in the east. Polyploidy, including triploidy with variable pollen sterility in two species, is shown to be a minor factor in the evolution of the tribe. As in other hardwood families, aneuploid change of base chromosome number has been important. In PuUenaea aneuploidy is associated with considerable morphological diversity, and ten groups of species are defined. Chromosome loss or gain was more frequent in regions where fluctuations in aridity had most profound effect, as in South Australia, while Victoria appears to have been a centre of survival and dispersal for most £c = 8 species. On morphological evidence, this was the basic chromosome number of the genus, while x -1 and x -^ apparently had multiple origins in both east and west. The pattern of rapid speciation suggested for one PuUenaea group may indicate that "catastrophic" evolution permitted the success of PuUenaea above the other genera with more stable chromosome number. Introduction The family Papilionaceae of the Legiiminosae comprises ten tribes according to Bentham (1864), but Hutchinson (1964) elevates most of Bentham's subtribes to tribes, bringing the total to fifty. The numerous genera are widely dispersed throughout both hemispheres in a great diversity of habitats and are well represented in Australia. In particular, the tribe Podalyrieae has shown extensive development in this country with 21 (according to Bentham (1864)) or 24 (according to Hutchinson (1964)) of its genera being endemic. In Ihe present paper an attempt is made to elucidate the probable evolution, or historical development, of the tribe Podalyrieae within Australia. The data from which the evolutionary inferences have been dev('lo[)''d iiirliidf ry(()l(>;^nc;il, riioi-phologica! and distributional analyses. * School of Biological Sciences, University of Sydney, New South Wales, 2006. Present address: Department of Genetics and Cellular Biology, University of Malaya, Kuala Lumpur, Malaysia. Pkockkdings of thf: Li^nk.an Socikty ok Nkav Socrir Walks, Voi,. 100, Part 2.