Geographic and climatic range sizes of Australian eucalypts and a test of Rapoport's rule

We present data on the geographic, latitudinal and climatic ranges of 819 species in the large Australian tree genus Eucalyptus L'Herit. The distribution of geographic range sizes is highly skewed, with 68% of species having ranges that cover less than 1% of the continent and only 3% of species having ranges covering more than 10%. The mean range size is 1.5% of the continent and the median 0.5%. At each latitude there is a wide scatter of geographic and latitudinal range sizes. Rapoport's rule, that range size increases with increasing latitude, was not supported. Mean range size peaks in the 20-25 degrees S latitudinal band; this pattern is affected by the shape of the continent but is not simply a consequence of it. Climatic range size, expressed in terms of mean annual temperature and rainfall, also peaks at about 25 degrees S. The mean, median, and frequency distribution of range sizes of arid zone species is similar to that of mesic species. Eucalypt species diversity is highest in the 30-35 degrees S latitudinal band; once again, this pattern is not simply a consequence of the shape of the continent. The frequency distribution of range sizes in the two main eucalypt suballiances, Symphyomyrtus and Monocalyptus, are not significantly different, although Symphyomyrtus contains all the species with range sizes covering more than 6% of the continent. Symphomyrtus species tend to occupy drier sites than Monocalyptus.