Fine-scale quantification of floral and faunal breaks and their geographic correlates, with an example from south-eastern Australia

摘要

Aim We introduce a method to quantify shared breaks in aggregate biotic distributions and their relationships to geographic variables. The method is based on quantication of distributional taxic and abiotic data that can be applied over multiple spatial scales. We aim to show biogeographic breaks and varying transition zones at a ne level of detail (5-km resolution) and develop an approach to assess existing bioregionalization schemes. Location Global applicability, using an example from New South Wales in south-eastern Australia. Methods Moving window analyses, rotated in 15 increments through 360, are used to assess the degree of anisotropic spatial turnover between sets of gridded cells containing georeferenced species observations. Patterns of biotic turnover are compared with equivalent analyses for elevation and lithology. Identied breaks are assessed against an existing bioregionalization scheme (Interim Biogeographic Regionalisation of Australia, IBRA). Results There was ne-scale concordance between turnover patterns and several IBRA bioregions. Breaks in turnover of ora and fauna corresponded with the boundaries of the Hunter Valley and Sydney Basin regions, particularly the boundary between the Brigalow Belt South and Sydney Basin. Low-turnover zones were quantied; prominent examples are the Sydney Cataract and Wyong bioregions. Turnover along many boundaries was gradational, conrming that mapped breaks are not abrupt. A previously unidentied break was identied in the South East Corner bioregion. Spatial turnover patterns were similar between biota and were reected in mean correlation coefcients between turnover in each group: mammals–reptiles (r = 0.70, P 0.01); mammals–ora (r = 0.56, P 0.01); and reptiles–ora (r = 0.51, P 0.01). Generally, patterns of abiotic turnover reected biotic turnover, although mean turnover correlations were weaker than between biota. Main conclusions Using this method we were able to characterize taxic breaks and overlaps in detail and at a spatially ne resolution. For our study region, we conrm the overall integrity of the IBRA framework, but suggest that it may benet from revision in some respects.