Mass extinctions hit large vertebrates hardest

Washington DC: For animals, being huge comes at a price as a new study has found that mass extinctions don't favor large vertebrates.

The study finds that, similar to the mass extinction that's underway now, the end-Devonian extinction resulted in the loss of most large-bodied vertebrates. The results add support to the disputed Lilliput effect, which suggests a temporary size reduction in species occurs after mass extinction.

The Devonian mass extinction that occurred 359 million years ago is one of the most severe extinctions in history, resulting in the loss of more than 96 percent of species and the restructuring of whole ecosystems.

To gain more insights into patterns of survival and mortality, Lauren Sallan and Andrew Galimberti assembled a database of 1,120 body lengths for Devonian-Mississippian vertebrates.

They found that leading up to the mass extinction, vertebrates were consistently increasing in size; yet in the period following the extinction event, vertebrates consistently experienced reductions in body size.

Along with the dwarfing of surviving Devonian lineages, the reduced-size effect was found in news forms that evolved (e.g., ray-finned fishes and tetrapods), for the next 36 million years.

Large vertebrates tend to have lower reproductive rates and longer lifespans, which can make adaptation over a short period of time very difficult. Thus, the authors suggest that the relatively fast reproductive rates and shorter lifespans of small vertebrates are major contributing factors to their success following mass extinction events.

This research appears in Science.