Reef fish diversify faster

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American and Canadian scientists have found evidence that fishes living in coral-reef habitats undergo higher rates of diversification than similar groups living in other habitats.

The study by Michael Alfaro, Francesco Santini and Chad Brock, is published in the latest issue of the journal Evolution, and uses tetraodontiform fishes (pufferfishes and their allies) as an example.

The authors first examined the phylogenetic relationships of 67 tetraodontiform species using 2768 base pairs of two mitochondrial (12S and 16S) and one nuclear (RAG1) gene fragment.

The authors next applied a series of fossil calibrations on the resulting phylogeny and calculated divergence time estimates for the nodes and diversification rates for the various lineages using statistical methods.

Finally, the influence of reef association on diversification rates was tested by calculating the fraction of reef-associated species within each tetraodontiform family, and statistical methods used to test for correlation between the diversification rate and reef habitat.

The authors found that tetraodontiform lineages associated wih reef habitats generally experience greater rates of diversification than nonreef-associated lineages.

In addition, the authors found that the pattern of diversification is complex and does not suggest an ancient reef-fish association, but coincides with reef diversifiacation and marine provincialization during the late Oligocene (about 25 million years ago).

The authors argue that this increase in diversification rate is due in part to the ecological opportunities provided by the unique and complex reef habitat, and in part by major paleoclimatic events that have increased diversification rates in reef clades by fragmenting reef biotas.

For more information, see the paper: Alfaro, ME, F Santini and CD Brock (2007) Do reefs drive diversification in marine teleosts? Evidence from the pufferfishes and their allies (Order Tetraodontiformes). Evolution 61, 2104"2126.