For millions of years, wall lizards in Italian populations had three varieties; animals with a white, yellow or orange throat (the bottom three in the photo). The palette was balanced. Sometimes there were more orange specimens and other times the white ones were in the majority. But the different colors never displaced each other.
Biologists discovered in previous research that the throat color of these reptiles is determined by two genes that determine which and how much pigment is produced in the pigment cells.
But in central Italy the color variation suddenly ended. The red and yellow variants are virtually extinct, and the disappearance of that color variation is now also spreading to Alpine lizard populations in the north of the country. The polymorphism disappears, researchers write this month Science.
The cause is the arrival of “the Incredible Hulk” (in the photo above), as biologists from Lund University (Sweden) previously described the new variant in a press release mentioned. The “Hulk” is larger and greener and behaves more aggressively than the original wall lizards. The variant was caused by a new mutation in a completely different gene than the genes that produced the original pigment. It has changed the course of the lizard’s evolution.
In the article Science the researchers describe this new form more scientifically as wall lizards with the ‘nigriventris syndrome’, or black belly syndrome. The males with a nigriventris profile are dominant in their behavior compared to competitors with the ancestral profile. Over time, this form has become predominant through sexual selection.
The researchers think that the newcomer has disrupted social communication during mating, so that belly color no longer plays a role in mate choice. According to them, this explains why the yellow and orange variant disappeared while the white form continued to exist.
The journalistic principles of NRC