Deep star shift: Turnover of bathyal brittle stars (Ophiuroidea) across Australia and New Zealand

Background/Question/Methods

The deep sea in increasingly being exploited for fisheries and mineral resources. Describing and visualizing turnover of deep-sea (200-2500 m) biodiversity is urgently required by government and international agencies for area-based conservation and resource management. Despite thousands of research expeditions, our knowledge of large scale biogeography in the deep sea is largely based on qualitative analyses or environmental surrogates. A method of mapping turnover based on statistical analysis of distribution data has remained elusive. This study examined beta diversity of brittle star species (Ophiuroidea) across Australia and New Zealand, based on modelled distributions. The nature of data available from the deep-sea severely restricts the types of analyses available for use. Here we use a ‘predict and then assemble’ approach to determine regional and inter-regional changes in species composition.

Results/Conclusions

Our results suggest the presence of transitional zones rather than abrupt biogeographical breaks. Primary production regimes and oceanographic currents, rather than sea surface temperature (solar radiation), appear to be driving latitudinal turnover. Regions of high dissimilarity change drastically depending on the scale at which turnover is modelled, reflecting the contrast between local turnover and regional uniqueness. Models of turnover will help describe biogeography in the deep-sea and contribute to developing a strategy for broad-scale spatial prioritization for bathyal marine ecosystems.