A team of Argentinian researchers has provided an innovative insight into the transformation of cetaceans such as whales, dolphins, and porpoises over the last 50 million years. By analyzing the evolution of species and their roles within ecosystems, they have revealed that these components have not always advanced in tandem.
Reconstruction of Cetacean Evolution
The study, conducted by experts from the National Scientific and Technical Research Council (CONICET) and the National University of La Plata (UNLP), was published in the prestigious Nature Communications. The analysis suggests that the evolution of cetaceans, which were once terrestrial creatures, is one of the most fascinating in mammalian history.
Starting from a broad fossil record, the team reconstructed how cetaceans changed their locomotion, diet, and auditory capabilities to adapt to different aquatic environments.
The study included 127 current and extinct species, among them 11 archaeocetes, 26 mysticetes, and 90 odontocetes. Using an “ecological space” model, the researchers evaluated ecological niches based on variables such as body size, dentition, and habitat.
Along with taxonomic diversity, the experts investigated ecological disparity, a concept that measures how different species adapted and performed their roles within marine ecosystems.
According to researcher Mónica Buono, this dual approach allowed for an understanding of how ecological variables influenced evolutionary success, establishing relationships between species diversity and their time of appearance.
Key Moments in Cetacean Evolution
The research identified three critical phases: the first, from the Eocene to the Oligocene, marked the transition from primitive cetaceans to neocetes. The second moment, during the late Oligocene to early Miocene, witnessed the evolution of mysticetes and the diversification of odontocetes. Finally, the Plio-Pleistocene saw the extinction of ancient lineages and the emergence of modern cetacean biodiversity.
A crucial finding was the decoupling observed between the number of species and functional diversity. Although the number of species decreased during the Pleistocene, functional variety remained constant. Ecological niches left by extinct species were occupied by other cetaceans or marine tetrapods, such as pinnipeds.
The study concludes that biological innovations and environmental changes affected each evolutionary stage differently, highlighting the influence of biological factors in the initial transition and climatic factors in later diversifications.
