When trying to understand the present, it is helpful to look at history. New research from the University of Nebraska-Lincoln examined the fossil record dating back 66 million years, tracking changes in mammal ecosystems and species diversity on the North American continent.
The study, led by Alex Shupinski, who received her PhD in May, and co-authored by Kate Lyons, associate professor in the School of Biological Sciences, provides a large-scale picture of how species diversity changed over the first 65 million years of history from nature. the Cenozoic Era – until the arrival of humans – and how climate and other environmental factors, including changing landscapes, affected animal life on the continent.
The findings published in Proceedings of the Royal Society B also offer a glimpse of how mammals recovered after the last mass extinction: the extermination of non-avian dinosaurs.
“66 million years ago we start from a completely subtropical environment in North America to grasslands to a frozen savannah, and eventually we reach the ice age,” Shupinski said. “It shows how species have changed over time, through many ecological, ecological and climatic changes, and it allows us to compare these events and across different spatial scales.”
The researchers sliced the Cenozoic fossil record into million-year increments and used three indices of functional diversity – which quantify changes in community structures using mammal traits – to examine mammal communities at both local and continental scales.
For most of the Cenozoic, local and continental measures of functional diversity differed, but surprisingly, for the first 10 million years of the epoch, immediately after the extinction of non-avian dinosaurs, all measures of functional diversity, both local and across, remained the whole world, the same. continent, increased.
“That was fascinating to see that for most of the Cenozoic, functional diversity was decoupled across temporal and spatial scales, except this one time,” Shupinski said. “Over 10 million years, all measures change in the same way. Then, about 56 million years ago, we get this massive immigration of mammals from other continents into North America, and at that point we see a divergence of functional diversity. .
“Communities change at different times, at different rates and in different directions,” she said. “We may see diversity of roles increasing locally, but continentally they are decreasing.”
Lyons said some of the changes among mammal species can be explained by environmental changes, including periods of cooling and warming or when heavily forested areas were taken over by grasslands, but that the large-scale environmental changes did not reach the level of disruption that was reported caused by the mass extinction of dinosaurs.
“That’s why this could potentially be a way to pinpoint parts of the world or communities that are under particular pressure,” Lyons said. “We may be entering a sixth mass extinction event, and if so, we can expect communities at the forefront of that extinction to respond in a similar way, based on the patterns we see after the extinction of the non-avian dinosaurs . .”
In the field of conservation paleobiology, tracking changes in past ecosystems over long periods of time helps scientists and the public better understand the biodiversity crises occurring today. This current study provides an in-depth analysis of the age of mammals and hints at what might happen next.
“If we look at the modern (crises) and we see a similar response in the functional diversity of modern community structures, this can be a tool for conservation because we can highlight some of these communities that are experiencing the most unrest and are in the problems are located. highest risk of change and disruption of their ecological services and function,” said Shupinski.
Other authors of the study include Peter Wagner, professor of earth and atmospheric sciences at Nebraska, and Felisa Smith of the University of New Mexico, Albuquerque.
