New species formed when the Mediterranean dried up – sciencedaily
A new study may have uncovered why wall lizards have become the most successful reptile in the Mediterranean region. The results reveal how drastic changes in sea level and climate 6 million years ago affected species formation in the region. Researchers believe they can now explain why lizards have become so diverse and widespread, which has puzzled biologists since the 19th century. The study is published in Nature Communication.
The evolution of wall lizards offers clues as to how major events in Mediterranean climate and geology millions of years ago affected species formation or extinction, and also paved the way for the biodiversity.
The wall lizards are around 20 million years old. However, species formation appears to have accelerated shortly after the Messinian salinity crisis 6 million years ago. During this period, the Mediterranean almost dried up, only to quickly fill with water again when the Strait of Gibraltar opened.
“Our results show that the dramatic changes back then likely contributed to the emergence of new species. They also shed light on why biodiversity looks like it is today,” says Tobias Uller, professor of evolutionary ecology at Lund University who led the international study study.
Research indicates that species isolated from each other for millions of years have sometimes found each other and shared genes. By comparing the DNA sequences of 26 species and 8 subspecies, the team succeeded in mapping the main evolutionary characteristics of wall lizards. This included which parts of the genome were transferred from other species by hybridization.
One example is the wall lizard found in Ibiza. Half of their genes come from the wall lizards that live today in the Iberian Peninsula, and the other half from those found in the Balkans and among the Greek islands. The Ibiza species is therefore originally a hybrid, which has provided evolution with great opportunities to combine old genes in new ways.
According to the researchers, this probably explains why species like the Ibiza wall lizard have such remarkably variable coloration: Despite close relationships and geographic proximity, they are one color on an island, but of a variety of colors on the next one, for example.
“We believe that hybridization has fueled evolution, promoting biodiversity and the extraordinary adaptability of certain species,” concludes Tobias Uller.