Here’s What People Are Saying About Lizards

Why are there so many lizards? Why are they so diverse? Why are there so many species that only live in the Mediterranean basin? A new study has answered these questions about the most common elusive reptiles in our neighborhood.

At some point in the history of the world, those abundant familiar reptiles, more than 26 species of lizards, conquered the Mediterranean coasts. They were born in a dramatic moment, when the sea that bathes us, always threatened by excessive salinity, dried up.

Lizard is a vulgar name. Thus we know a large part of the more than 26 species that is part of the genus Podarcis (a type of scaly reptiles). Normally the lizards are small (20-25 cm) and a great majority are endemic to the Mediterranean.

The lizard’s body is covered in scales and its highly regenerative tail is often among the first astonishes of a girl or a boy in nature. The tail continues to move once it has been plucked, which serves to flee from possible predators.

Some species of  Podarcis are extraordinarily variable, as illustrated by this panel showing representative males from six different populations of Podarcis pityusensis, an endemic species to Ibiza, Formentera and adjacent islets.

Different types of lizards
Photo credit: pityusensis Day’s Edge Productions (top left, center right, bottom left) and Mike Zawadzki (top right, middle left and bottom right)

A new study has discovered why 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 the evolution of different species in the area.

Researchers may explain why lizards became so diverse and widespread, something that has puzzled biologists since the 19th century. The study has been published in Nature Communications.

The Mediterranean basin is a biodiversity hotspot, driven by climatic oscillation and geological change over the last 20 million years.

The abundance of lizards

The lizards of the genus Podarcis are among the most abundant, diverse and conspicuous Mediterranean fauna. For the study, they have sequenced the genomes of 34 major lineages spanning 26 species. And they have discovered an early separation into two clades centered on the Iberian and Balkan Peninsula, and two clades of endemic Mediterranean islands.

Diversification within these clades occurred between 6.5 and 4.0 million years ago, a period spanning the Messinian salinity crisis, during which the Mediterranean Sea nearly dried up before rapidly filling up again.

The evolution of lizards offers clues as to how major Mediterranean geological and climate events millions of years ago affected the way species formed or became extinct, and also paved the way for biodiversity.

A dry sea until the strait of Gibraltar opened

Lizards date back about 20 million years. However, species formation accelerated shortly after the Messinian salinity crisis 6 million years ago. During this period, the Mediterranean nearly dried up, only to quickly fill with water again when the Strait of Gibraltar opened.

“Our results show that the dramatic changes at that time probably contributed to the emergence of new species. They also shed light on why biodiversity looks today, ”says Tobias Uller, professor of evolutionary ecology at Lund University, who led the international study.

They hybridiszed

Research indicates that species isolated from each other for millions of years occasionally found and shared genes. By comparing the DNA sequences of 26 species and 8 subspecies, they have found which parts of the genome were transferred from one species to another through hybridization.

An example is the endemic lizards of Ibiza. Half of its genes come from the lizards that today live in the Iberian Peninsula, and the other half from those found in the Balkans and between the Greek islands.

Thus, the species in Ibiza originated as a hybrid, providing evolution with great opportunities to combine old genes in new ways.

Types of lizards
Photos of representative male phenotypes of six Podarcis species: P. siculus (top left), P. filfolensis (top right), P. erhardii (middle left), P. tauricus (middle right) , P. waglerianus (lower left) and P. muralis (lower right). . Photo credits: Birgit and Peter Oefinger

According to the researchers, this probably explains why species like the Ibiza lizards are so surprisingly variable in coloration: despite close relationships and geographic proximity, they are one color on an island, but a variety of colors on the island. following.

“We believe that hybridization has driven evolution, promoting biodiversity and the extraordinary adaptability of certain species,” concludes Tobias Uller.

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