The teleost fishes are stunningly diverse, accounting for nearly half of all vertebrate diversity.
One hypothesis used to explain this extraordinary diversity is that a fish-specific whole-genome duplication event (FSGD) in the ancestor to teleosts triggered their subsequent radiation.
Francesco Santini, Luke Harmon, Giorgio Carnevale and Michael Alfaro test this hypothesis in a study published in a recent issue of the journal BMC Evolutionary Biology.
They did so by studying the diversification rates of teleost fishes using a large-scale molecular timescale for ray-finned fishes that allowed the estimation of the divergence times of most major lineages as well as the origin of many groups within them.
The authors used 227 vertebrate RAG1 (a nuclear gene) sequences to infer divergence times with the ages of 44 clades constrained by fossils.
They then used mathematical models to test whether or not diversification rate shifts supports the FSGD-diversification hypothesis (which predicts that diversification rates in teleosts increased soon after the acquisition of a duplicated genome).
Although the authors showed show that one of three major diversification rate shifts within ray-finned fishes occurred at the base of the teleost radiation, as predicted by the FSGD hypothesis, they also found evidence that the FSGD itself may be responsible for a little over 10% of living teleost biodiversity.
The authors conclude that "...the causes of diversification in large clades are likely to be complex and not easily ascribed to a single event, even a dramatic one such as a whole genome duplication."
For more information, see the paper: Santini, F, LJ Harmon, G Carnevale and ME Alfaro (2009) Did genome duplication drive the origin of teleosts? A comparative study of diversification in ray-finned fishes. BMC Evolutionary Biology 9, 194 doi:10.1186/1471-2148-9-194.