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Why was South America once a biological island? How did ancient animals evolve their unique forms?
South America's biodiversity has undergone astonishing changes over the past millions of years. The local ecosystem has long been isolated from other continents, resulting in unique flora and fauna. During the changes in geological time, this land has shown its mysterious evolution process, especially about 2.7 million years ago, with the emergence of the Isthmus of Panama, creatures in North and South America began to communicate on a large scale. This phenomenon is known as It is called "Great American Biological Exchange (GABI)". This article explores why South America became a biological island throughout history and how ancient animals evolved their unique forms.
The isolated history of South America
Since the late Mesozoic, South America has shown "brilliant isolation" due to its geographical isolation from other continents. This history allowed the animal kingdom of South America to develop many unique species that do not exist anywhere else on Earth, many of which are now extinct.
The ancient mammals of South America include a variety of non-true mammals (such as monotremes and other ancient types), as well as a group of native ungulates called "Meridiungulata".
The expansion of the ocean and its consequences
About 40 million years ago, South America began to experience a series of biological invasions, with many animals crossing over from other continents, possibly via oceans, driftwood, or other oceanic islands. These invaders included rodents from Africa, whose arrival transformed South American ecosystems and encouraged further diversification of native species.
For example, the rapid diversification of Caviomorph rodents from Africa in South America led to the emergence of diverse species including capybaras and hedgehogs, which later became important organisms in South America.
The impact of biological exchanges in Great America
With the emergence of the Isthmus of Panama, biological exchanges between the two continents reached their peak. Many North American mammals, such as horses and moose, as well as carnivorous mammals such as leopards and dogs, began to move south, causing profound impacts on South American ecosystems.
South American species that migrated from south to north became less successful in competition, and most were unable to occupy their ecological niches efficiently, whereas North American species were able to successfully colonize and expand.
The formation of unique shapes
Due to the long-term isolation and special evolutionary history of South America, many animals have developed unique forms. For example, the ground sloths and giant ground sloths of South America were among the largest herbivores during that period, and their morphological structures were particularly unique among megafauna.
In addition, moas, a type of giant flightless birds, appeared in South America. These birds may have filled the ecological niche of animal predators.
Conclusion
The uniqueness of South America and the evolution of its ancient species paint a wonderful ecological picture. The Great American biological exchange not only changed the ecosystem of South America, but also demonstrated the power of species evolution and adaptation. We are still thinking about how the future of this land will be reshaped, and what will new creatures and species look like?
