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Taxonomic distinctness of coastal fishes around the rim of the South Indian Ocean

Beckley, L.E., Clarke, K.R. and Somerfield, P.J. (2009) Taxonomic distinctness of coastal fishes around the rim of the South Indian Ocean. In: AMSA2009 46th Annual Conference for the Australian Marine Sciences Conference, 5 - 9 July, Adelaide, Australia.


Indo-Pacific biogeography has often been explored relative to the Indo-Australian Archipelago centre of origin with southward dispersal of Indo-Pacific fishes in the Indian Ocean linked to poleward-flowing boundary currents off Australia and Africa. Coupled with early Gondwanan fragmentation, which largely defined the biogeography of temperate southern hemisphere taxa, the mixture of fishes around the rim of the South Indian Ocean provides an interesting test case for broad-scale biodiversity analyses. Existing presence/absence data-bases of fish distributions from South Africa and Western Australia were examined and well-defined biogeographic patterns were evident. When compared, the fishes of north-western Australia and north-eastern South Africa were most similar and maximum divergence was evident between the south coasts of Australia and Africa. Although, as expected, species diversity declined from north to south, the number of families across the latitudinal range was surprisingly consistent. The relatedness of fishes across the Indian Ocean was investigated using taxonomic distinctness measures (i.e. distances travelled in connecting every pair of species via a fixed set of levels in the hierarchical Linnean taxonomic tree). Average taxonomic distinctness (Δ+) and variation in taxonomic distinctness (Λ+), known theoretically to be insensitive (in mean value) to variation in sampling effort, both increased from north to south. Comparisons of these values with simulations of their expected range under random sampling at different intensities (‘funnel plots’) indicated, for the south coasts of Australia and Africa, that average taxonomic distinctness consistently exceeded the 95% upper limit of the simulations. This finding, of greater than expected taxonomic breadth, is largely unprecedented in the literature on observed patterns in taxonomic distinctness, emphasising the high, and unusual nature of, fish diversity in these regions.

Publication Type: Conference Item
Murdoch Affiliation: School of Environmental Science
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