Saturday, May 7, 2011

Ray Fish Species Evolution

The Ray Fish or Actinopterygii (ray-finned fishes) is the largest and most diverse vertebrate group, but little is agreed about the timing of its early evolution. Estimates using mitochondrial genomic data suggest that the major actinopterygian clades are much older than divergence dates implied by fossils. Here, the timing of the evolutionary origins of these clades is reinvestigated using morphological, and nuclear and mitochondrial genetic data. Results indicate that existing fossil-based estimates of the age of the crown-group Neopterygii, including the teleosts, Lepisosteus (gar) and Amia (bowfin), are at least 40 Myr too young.

Ray Fish

We present new palaeontological evidence that the neopterygian crown radiation is a Palaeozoic event, and demonstrate that conflicts between molecular and morphological data for the age of the Neopterygii result, in part, from missing fossil data. Although our molecular data also provide an older age estimate for the teleost crown, this range extension remains unsupported by the fossil evidence. Nuclear data from all relevant clades are used to demonstrate that the actinopterygian whole-genome duplication event is teleost-specific. While the date estimate of this event overlaps the probable range of the teleost stem group, a correlation between the genome duplication and the large-scale pattern of actinopterygian phylogeny remains elusive.

Ray Fish

More than half of all vertebrates are ray-finned fishes. The total number of species is now approaching 27 000, the vast majority of which are teleosts (Nelson 2006). Teleosts include numerous ecologically and economically important groups, as well as model organisms used for genomic and developmental biology research. Accurate estimates of actinopterygian divergence dates are therefore vital for addressing fundamental questions about the origin of modern vertebrate biodiversity and for making meaningful interpretations of experimental data. However, theories about the timing and pattern of the early evolution of rayfinned fishes are in a state of disarray and lag far behind our understanding of tetrapod evolution.

Ray Fish


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