About 15 million years ago, the favoring large herbivores — which could weigh more than a ton — and decrease in the number of medium-sized prey were decisive factors for the extinction of carnivorous predators .
A study, led by scientists from the State University of Campinas (Unicamp) and with the participation of institutions from Spain and Sweden, reconstructed the conditions of this period in detail to discover how extinctions can generate a cascade effect. It was published in the journal Ecology Letters in May of this year.
The Iberian Peninsula, a territory that today encompasses Portugal and Spain, was a paradise of biodiversity around 20 million years ago. Animals similar to those that today constitute the African megafauna – for example, Iberian and older versions of today’s rhinos, elephants and felines – grazed or hunted in environments with many species of prey and predators.
Around 15 million years ago, however, a sharp drop in temperatures, combined with an increasingly arid climate, changed the landscape. Vegetation became more open, to the detriment of closed forests. This favored large herbivores, which prospered while their medium-sized counterparts became extinct. As a result, the availability of prey for carnivores also decreased. It was harder to hunt animals such as gomphotheres, which were 3 meters tall and weighed more than 2 tons (a relative of the elephant that had four tusks) than deer, which weighed up to 30 kilos, for example.
The study reconstructed and analyzed the largest time series of food webs to date, from 20 million years ago to the present. The analyses were made possible by the most complete database of mammals from the period, compiled from the fossil record of the region, one of the best studied and comprehensive in the world.
The Iberian Peninsula is known for the abundance of fossils of its extinct fauna, which has allowed us to understand how ecosystems changed and how species evolved millions of years ago.
“The fossil records come from several paleontological sites. The database we analyzed contains the species composition of the region with very high resolution. For each group of animals, there is detailed information such as body size, type of diet, form of locomotion, etc. This made it possible to infer, for a given location, at a given time, who preyed on whom and how this changed over time,” explains João Nascimento, first author of the article and a FAPESP doctoral fellow at the Institute of Biology (IB-Unicamp).
“The goal of the project is to understand how ecological interactions can influence major evolutionary patterns, especially the emergence and extinction of species. The major difficulty with this type of study is that there is rarely any information on how species interacted in the past. The idea was to use statistical tools and mathematical models on fossil data to fill this knowledge gap,” says Mathias Pires, a professor at IB-Unicamp supported by FAPESP, who supervised the research.
Simplification
The process that occurred in the Iberian Peninsula over the course of 15 million years is known as the simplification of food webs, a phenomenon that is very common in current ecosystems. It is also known as homogenization, when a few generalist species replace the rare and specialist ones.
“Similarly, as we see in some current populations, we are witnessing a change in the composition of herbivore communities and the predators that feed on them. On an ecosystem scale, this has a much greater impact than the simple loss of one or another species,” Pires emphasizes.
As a result of changes in herbivore communities, the longevity of predators was directly related to their risk of extinction. Mathematical models showed that those with fewer prey available were the ones that disappeared from the fossil record more frequently over time.
“The role of ecological interactions in influencing extinction patterns over evolutionary time is clear. Therefore, we need to consider a larger ecological context to develop conservation strategies to preserve predators in their ecosystems,” said Fernando Blanco, co-author of the study and researcher at the University of Gothenburg in Sweden, in a press release.
According to the authors, the study highlights the need to conserve diverse prey populations to maintain other predator populations, maintaining structurally robust ecological networks.
“The extinction of one group of species has a cascading effect on others, which is extremely damaging to ecosystems and the services they provide. We have a unique opportunity to understand what happened in the past and what is happening now in order to intervene and prevent new extinctions from occurring,” Pires concludes.
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This content was originally published in Herbivore gigantism led to the extinction of predators 15 million years ago on the CNN Brasil website.
Source: CNN Brasil
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