With an ever-increasing number of species facing extinction, scientists are turning to the past to gain a clearer idea regarding the process and effects of mass extinctions, specifically in terms of the reaction of remaining species and ecosystems.
And while many studies thus far have argued that those who survived these massive die-offs were suddenly the recipients of untold ecological opportunities and an accompanying flourishing of new anatomical features, a new study published in the Proceedings of the Royal Society B suggests that this was not always the case.
Some, it appears, were simply unable to fully exploit the new opportunities than others.
The researchers, which represented scientists from the University of Lincoln, the Field Museum of Natural History in Chicago, the Museum für Naturkunde in Berlin and the University of Bristol, came to this conclusion after examining how a group of ancient relatives of mammals called anomodonts responded to largest mass extinction in Earth history.
In all, some 90 percent of marine organisms and 70 percent of terrestrial species became extinct during the end of the Permian Period some 252 million years ago, the effects of which were profound for those who remained.
"Groups of organisms that survive such a mass extinction are said to have passed through an evolutionary bottleneck analogous to the genetic bottleneck that may occur in a population if many of its members die off," lead study author Marcello Ruta of the University of Lincoln said in a press release. "At the population level, a genetic bottleneck sometimes allows the population to move to a new evolutionary trajectory, but other times it constrains the future evolution of the population."
Toward the end of the Permian Period, the researchers explain, there were a significant number of anomodont species that covered the spectrum in terms of body size and ecological adaptations, including everything from land-loving plant eaters to amphibious and somewhat hippo-like creatures.
However, while their numbers fluctuated during and then after the Permian period, their anatomical diversity saw a steady decline over their history, even after the majority of their peers had been wiped off the map.
"This suggests that the evolutionary bottleneck they passed through during the extinction constrained their evolution during the recovery," Ruta surmised.
Knowing this, the researchers argue, helps to better understand the reconstruction after major biological crises.
"The results underscore that recoveries from mass extinctions can be unpredictable, a finding that has important implications for the species extinctions being caused by human activity in the world today," co-author Michael Benton concluded. "We cannot just assume that life will return to the way it was before the disturbances."