The lizard Podarcis wallis nigriventris It may not reach a scary size or smash everything in its path, but evolution has turned this lizard into something of an Incredible Hulk – green skin included. P. nigriventris is something like the imposing Marvel superhero when compared to other species of wall lizard (Podarcis muralis). While the common variety is relatively small and brownish to greenish-brown, the nigriventris The subspecies, which occurs in central Italy, is visually impressive due to its green (more) skin with black markings, its larger size and increased aggressiveness.
A team of evolutionary biologists led by Nathalie Feiner from Lund University in Sweden wanted to find out which genes contribute to the development of P. nigriventris so huge. Like many fictional people with superpowers (but unlike the mutated Hulk), this lizard is a hybrid.
Giant hybrids
Although wall lizards occur from the Iberian Peninsula to Asia Minor, the researchers focused on lizards from populations in central Italy (IT lineage) and the southern Alps (SA lineage). These lineages most likely split from a common ancestor 5-6 million years ago and then began interbreeding – individuals from the different lineages mated with each other to produce hybrid offspring.
P. nigriventris originated as a subspecies of the IT lineage. However, some of its traits were passed down from the SA lineage. This is called introgression and occurs when genetic information is transferred from one lineage or species to another through hybridization. The traits the researchers focused on were coloration on the back and belly, lateral blue patches, body mass, and head length.
Because P. nigriventris Traits have found their way into the SA lineage through introgression, it can be difficult to say what is truly ancestral. It was initially thought that women who were P nigriventris Traits in men that increased their chances of finding a mate. However, some of these traits were later observed in women, so these traits are not unique to men competing for women.
“Various lines of evidence support the existence of [these traits] in both sexes and [the traits] remain intact during introgression into a distantly related lineage,” the researchers said in a recent study published in Science Advances.
The brownish one P. muralis are considered the original phenotype. To see how the nigriventris To develop this phenotype, Feiner would have to figure out where in the lizard’s genome the features that make up this phenotype are found.
Green genes
What Feiner and her team discovered when analyzing the lizards’ genome was that the features that P. nigriventris are determined by genes that regulate neural crest cells. These multipotent stem cells, which form early in the embryo, can transform into different types of more specialized cells throughout the embryo and contribute to everything from heart valves to coloration.
Such a gene, Rbm10, regulates the proliferation of neural crest cells, i.e. their growth and division, while another, Tfcp2l1, regulates how they differentiate into more specialized cells during embryo development. Yet another, Gpc3, is required for neural crest cells to migrate to different locations in the embryo where they integrate into tissue.
But where was the difference that would ultimately change the color scheme? nigriventris Phenotype? The answer lay in a region of a chromosome that contains a gene, known as Rab18, which also helps in the migration of neural crest cells. Rab18 And Acbd5 both play a role in pigment production. This could be related to the green-black coloring P. nigriventris.
“Gene flow analyzes showed that these [chromosomal] The region has probably migrated from the IT lineage into populations of the SA lineage that strongly express the nigriventris phenotype,” the researchers said in the same study.
While the exact factors that caused this green and black P. nigriventris Monsters (at least monsters next to hers P. Muralis Although the ability of representatives of different animal species (e.g. relatives) to develop different colorations to adapt to changes in their environment is still unknown, the origin of their appearance is no longer a mystery.
At least, unlike Bruce Banner himself, Hulk lizards don’t have to expose themselves to extreme radiation to maintain their size, color, and strength.
Scientific Advances, 2024. DOI: 10.1126/sciadv.adk9315