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<a href = "https://3c1703fe8d.site.internapcdn.net/newman/gfx/news/hires/2018/adaptableliz.jpg" title = "A male lizard from the lava flow Pisgah photographed five days after collecting on the ground (left) and the same lizard (right) after being housed for four months in the laboratory on pale sand. Current Biology, 2018 ">
A male lizard from the Pisgah lava flow photographed five days after harvest in the field (left), and the same lizard (right) after being housed for four months in the lab on clear sand. Credit: Corl et al. Current Biology2018
Lateral lizards in most of the Mojave Desert have brown and brown markings that blend well into their desert environment. On the Pisgah lava flow, however, there is a very different population of side-lizard lizards, as black as the rocks on which they live.
How do animals invade new environments different from those for which evolution equipped them with precise adaptations? Light-colored lizards on a lava flow should be easy to pick for predators, so how did they survive long enough to develop a darker color?
One of the explanations is that many of the traits of an animal are not fixed, but can change during one's life. This "phenotypic plasticity" allows individual animals to change their appearance or behavior to survive in a new environment. In the long term, new adaptations that promote survival occur in the population through genetic changes and natural selection, which affect the population over generations. This is known as the "Baldwin effect" after psychologist James Mark Baldwin, who presented the idea in a reference document published in 1896.
Scientists studying side-lizard lizards on the Pisgah lava flow have now documented this process in a meticulous way. They showed how individual lizards can change color in a new environment to become darker on the lava; they identified genes that regulate staining and differ between populations on and off the lava; and they found that genetic changes in the population suitable for lava flow make these lizards darker than others. Their conclusions, published on 6 September in Current Biology, can be the most detailed example of the Baldwin effect occurring in a wild population.
"It's an old and very powerful idea, and now we have genetic evidence of how it's going in nature," said co-author Barry Sinervo, professor of ecology and biology evolutionary at UC Santa Cruz.
Sinervo has been studying California side lizards for over 30 years. First author Ammon Corl, who earned his doctorate in Sinervo's lab, is now at the Museum of Vertebrate Zoology at the University of Berkeley. Corl said he first learned about the Pisgah lizard population from an unpublished doctorate. co-author Claudia Luke's thesis, now at Sonoma State University.
<a href = "https://3c1703fe8d.site.internapcdn.net/newman/gfx/news/hires/2018/1-adaptableliz.jpg" title = "The Pisgah lava flow in the eastern Mojave desert. Corl and Al., Current Biology, 2018 ">
Pisgah lava flow in the eastern Mojave desert. Credit: Corl et al. Current Biology2018
"Claudia understood how much their coloring is plastic and I tested the genetic changes that affected the coloring of the Pisgah population," said Corl. "Baldwin predicted that plasticity allows organisms to colonize new environments and then develop new adaptations through natural selection.However, until now, we lacked genetic tools to show that this was happening on the planet. ground."
When researchers move lizards laterally from one background to another (eg, sand to lava rock), color changes begin to appear within a week and gradual changes in coloring continue for months. "It seems that there is a slow and gradual accumulation of dark melanin pigment," said Corl.
The lizard populations on and off the lava flow have this plasticity allowing them to change color when they are moved into a new environment. But both populations also have inherited differences in pigmentation. The genetic analysis revealed differences between the two populations in two genes involved in the regulation of melanin production.
The researchers crossed lizards from both populations, reared offspring in a common environment, and measured offspring coloration. These experiments showed that variations in melanin-related genes correlate with the darkness of lizard skins.
Genetic sampling of side-lizard lizards surrounding the lava flow has shown that the genetic variants found in the lava population are limited to this population, suggesting that the variants result from mutations occurring in lizards living in the lava flow. washed. Demographic modeling studies have suggested that the new mutations occurred thousands of years after the lava flow about 22,000 years ago.
"We have been studying side-lizard lizards everywhere, even at another lava flow, and these genetic variants are only found in Pisgah, so we know where they appeared," Sinervo said. "These are the genes that govern staining by controlling the melanin production pathway, but in a complex way, the Pisgah lizards best match the color of the lava of any population." Background. "
The range of coloration possible for an individual lizard is remarkable. "In a way, it is amazing that natural selection always acts in the presence of such plasticity. All that is needed is a bit of discordance and this can make the difference between life and death, "said Corl. "There are still variations within the population, so we have opted for natural selection by acting on these genes.We can now conduct other field and laboratory studies to better understand how the characters evolve. highly plastic. "
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