title: The distribution of C3and C4grasses in Australia in relation to climate.
abstract: All but four of 833 native and 292 naturalised Australian grasses (Poaceae) have been assigned as having the C4or C4photosynthetic pathway. In conjunction with comprehensive species composition data for 75 geographic subdivisions Australiawide, this has permitted the construction of distribution maps for C3and C4grasses. C3and C4grass distributions have been considered (i) independently, using subdivisional native species numbers; and (ii) relatively, using 'subdivisional % C4'. C3species are most numerous in the Southern Tablelands (New South Wales), the QZ subdivision (Victoria), and Tasmania; C4species in the northern Northern Territory and northern Queensland, including the Cook subdivision where 54% of Australia's native C4grasses can be found. C3species predominate only in south-west Western Australia, parts of southern South Australia, the Tablelands, central and south coast, and south western slopes of New South Wales, Victoria and Tasmania. C4species predominate over 80-85% of the continental area. For 16 temperature and rainfall variables, subdivisional area-weighted means were calculated, and correlation analyses performed. C3species number correlates most highly with January average maximum temperature (-ve) and spring rainfall (+ve); C4species number with October average minimum temperature (+ve) and February median rainfall (+ve); '%C4' with January average minimum temperature (+ve). Predictive multiple linear regression equations were generated using climatic variables. In general, C4grass species, like C3species, increase in number with increasing rainfall, in their preferred temperature regime. C4species are most numerous where the summer is hot and wet; C3species where the spring is cool and wet. C4species numbers decline with decreasing temperature and/or decreasing summer rainfall; C3species numbers decline with increasing temperature and/or decreasing spring rainfall. Results are also considered in relation to the taxonomic and physiological heterogeneity of grasses and to Australia's geobotanic history.
authors.affiliation: Taxonomy Unit, Research School of Biological Sciences, The Australian National University, POB 475, 2601, Canberra City, A.C.T., Australia.
authors.forename: P W
authors.initials: PW
authors.lastname: Hattersley