Zoogeographic and Richness Patterns in Southern Ocean Benthos

Griffiths, Huw James (2010). Zoogeographic and Richness Patterns in Southern Ocean Benthos. PhD thesis The Open University.

DOI: https://doi.org/10.21954/ou.ro.0000f201


This thesis describes the large scale biogeographic patterns found in the Southern Ocean benthos. Using SOMBASE and SCAR-MarBIN, the two most comprehensive, georeferenced databases of Antarctic marine biodiversity ever compiled, a range of taxa were investigated but focusing on the Mollusca, Bryozoa and Pycnogonida. Over 8,000 species of marine invertebrates from over 5,000 sites constituting -34,000 records were used in the analyses.

The strong faunal links between the Antarctic and South America were confirmed but I found little evidence for a biogeographical relationship between the Antarctic or South America and New Zealand or Tasmania. Regional levels of Southern Ocean endemism proved the influence of the Antarctic Circumpolar Current upon the distribution of Southern Ocean benthos. My study shows the Southern Ocean as a ‘single functional unit’ with no evidence for an earlier proposed biogeographical split between East and West Antarctica. Some general rules on Antarctic benthic biogeography are viable, including species endemism rates of around 50% and a definite distinction between the sub-Antarctic islands influenced by either South America or by New Zealand.

In the context of potential shifts in species distribution with climate change I investigated the current ranges of selected Southern Ocean taxa (Mollusca, Amphipoda, Ophiuroidea and Hexacorala), and looked for hotspots of coinciding northern and southern geographic range limits. Southern Patagonia, South Georgia and Kerguelen had the greatest range-limit hotspots. Monitoring range shifts in these key places and taxa will enable us to track the influence and effects of climate change on benthic species distributions in the Southern Ocean.

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