The rich diversity of species on land is nothing new: the level of biodiversity has not changed much over the past 60 million years, shortly after the extinction of the dinosaurs. According to a new study from the University of Birmingham, the number of species on land has increased irregularly.
Previously, experts were sure that biodiversity is progressively increasing over geological time, that is, now the species are more diverse than they were tens of millions of years ago. But creating an accurate picture of how animals evolved and developed is not an easy task, if only because the fossil skeletons that archaeologists find become less and less complete over time. However, technology does not stand still: using modern computational methods, with the help of which it is possible to analyze hundreds of thousands of fossils, patterns that run counter to the generally accepted point of view begin to emerge.
Researchers at the University of Birmingham, along with other researchers from the US, UK and Australia, were able to study fossil data collected by paleontologists over the past 200 years. Scientists have focused their attention on terrestrial vertebrates - the earliest appearance of this group is determined almost 400 million years ago.
In the course of their work, the specialists determined that the average number of species in the ecological communities of terrestrial vertebrates did not increase for tens of millions of years. Their results, published in the journal Nature Ecology & Evolution, show that interactions between species, including competition for food and territory, limit the total number of species that can exist simultaneously.
“Modern experts generally believe that biodiversity has been increasing chaotically over millions of years, and that modern diversity is much better than the past. However, our results suggest the opposite: the number of species within terrestrial communities is limited for long periods of time. Now our task is to find out the reasons for this phenomenon,”says lead author of the study, Dr. Roger Close (Roger Close).
Among the various factors that keep diversity at its level, scientists say that the food and space that animals need are limited. The struggle for these resources can stop the penetration of new species into ecosystems, maintaining harmony between the intensity and speed of new species formation and animal extinction. At the same time, in the event of a large extinction of species due to one or another catastrophe, the diversity of species may begin to increase at a rapid rate, after which long periods of stagnation will again follow.
According to scientists, the most intensive development of diversity among terrestrial vertebrates occurred just after the global catastrophe that wiped out the dinosaurs 66 million years ago. In just a few million years (a fairly short period of time on this scale), biodiversity has increased two to three times compared to the level that was on the planet before the disaster. The main merit in this, according to Close, belongs to modern mammals.
“Our work is an example of the combination of fossil power and advanced statistical approaches to answer key questions about the origins of modern biodiversity. By understanding how biodiversity has changed in the past, we could examine the likely long-term impact of the current biodiversity crisis,”says co-author Professor Richard Butler.
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Dmitry Mazalev