Assessment of an ecoregion approach for classifying macroinvertebrate assemblages from streams in Victoria, Australia

Abstract

An interim biogeographic regionalization for Australia (IBRA) divided the state of Victoria into 10 ecoregions or zones. The degree to which differences in the composition of stream macroinvertebrate assemblages (at 199 sites throughout the state) matched this a priori regionalization was determined by analysis of similarities (ANOSIM) of Bray–Curtis similarity measures. ANOSIM showed that although there was some overall difference in macroinvertebrate composition among the 10 ecoregions only 3 of the individual zones could be considered to have compositions that distinguished them from other zones. The remaining IBRA zones covered ∼60% of Victoria, but showed few differences in composition. The levels of difference in assemblage composition between the 25 catchments within Victoria or between the 11 site groups derived from cluster analysis were clearly greater than that for the IBRA zones. Thus IBRA does not provide a reliable classification of macroinvertebrate assemblages in Victoria.