Marine bioregions in Australia: numerical analysis of provinces on the east coast

Bioregions, distinct ecological assemblages of flora and fauna, have long been used to aid conservation decisions. Bioregions containing at-risk taxa have routinely been recommended for assignment as Marine Protected Areas (MPA). However, the number, location and extent of bioregions in Australia has been heavily debated over the previous few decades. The current consensus, based on coastal fishes, does not take into account the diverse benthic taxa present. A large dataset of Australian east coast molluscs, assembled from museum collection records of the last 100 years, was analysed to identify bioregions. Latitudinal bands were analysed with an array of methods previously utilised to identify bioregions elsewhere in the world. The number and size of provinces from each method were compared to form a consensus. Faunal turnover was high and consistent across the entire geographic extent, with no distinct separations into bioregions. There was strong support for a distinct Victoria/Tasmania province. Nitrate content, showed the strongest control over southern latitudes and it is likely this province is controlled by nutrient availability. These results suggest that Australian mollusc distributions are potentially controlled by oceanic currents and nutrient supply from southern waters, with the Bass Strait forming the only distinctive distribution control.