Can we detect adaptive radiations in marine fishes?

The concept of adaptive radiation, according to which a biological lineage undergoes elevated rates of species diversification while at the same time experiencing divergence along ecological axis, is often invoked in evolutionary studies to explain the astonishing diversity of groups such as the cichlids of the African rift lakes, silverswords plants and honeycreeper birds in Hawaii, and anole lizards in the Neotropics. Recent surveys of the scientific literature, however, revealed that most studies of adaptive radiation do not recover the expected signal of early burst of lineage diversification, and in several animal groups rates of cladogenesis and phenotypic evolution may often be unlinked, thus creating complex patterns in the tempo of lineage and trait diversification. Furthermore, in spite of the dramatic increase in number of studies of the tempo and mode of evolution in marine fishes during the past decade, very little evidence has been uncovered to support the idea that adaptive radiations played a role in generating their staggering diversity, and even when a signal of radiation is recovered this virtually never conforms to the “traditional” early burst scenario. Using examples from our research on diverse groups of marine teleost fishes such as jacks and allies (Carangoidei), pufferfish and allies (Tetraodontiformes) and snappers (Lutjanidae), we will discuss why it is so difficult to recover a signal of adaptive radiation in general, and early burst in particular, and offer some suggestions on how to test for these patterns.