The rise and fall of climate change over the past 65 million years has had a continuing effect on the fauna of the North American continent, according to a new study which identified six distinct waves of mammals, known as “evolutionary fauna.”
“Although we’ve always known in a general way that mammals respond to climatic change over time, there has been controversy as to whether this can be demonstrated in a quantitative fashion,” said Brown University evolutionary biology Professor Christine Janis. “We show that the rise and fall of these faunas is indeed correlated with climatic change – the rise or fall of global paleotemperatures – and also influenced by other more local perturbations such as immigration events.”
Janis and her colleagues described their findings online this week in the journal Proceedings of the National Academy of Sciences, showing that four waves of species diversity showed statistically significant correlations with major changes in temperature, while the remaining two – though weaker – still showed some correlation, but also corresponded to an influx of mammals from other continents.
The authors of the study found in their research six distinct and consecutive groups of mammal species that shared a common rise, peak, and decline in their numbers.
One example is the “Paleocene fauna,” which had largely disappeared, making way for the “early-middle Eocene fauna” by approximately 50 million years ago. On top of that, the transfer of dominance correlated with temperature shifts.
Not only do the numbers add up, but the story behind the numbers makes sense as well. One example shows a change after a warming episode some 20 million years ago in the early Miocene epoch which changed the dominant vegetation from woodland to savannah-like grasslands. As a result, it is no surprise that many of the herbivores that made up the “Miocene fauna” had high-crowned teeth that would allow them to eat the foods provided by the savannah-like environment.
A study such as this does not allow for future predictions, said Janis, but it does make clear that climate change has had an impact on fauna previously.
“Such perturbations, related to anthropogenic climatic change, are currently challenging the fauna of the world today, emphasizing the importance of the fossil record for our understanding of how past events affected the history of faunal diversification and extinction, and hence how future climactic changes may continue to influence life on earth,” the authors wrote in the paper.
Source: Brown University
Image Credit: Courtesy of Carl Buell