Why do some lizards flash bright colors from their throats? In many animals, bold colors are more than just decoration—they’re a way to send signals to others, whether to attract a mate, ward off a rival, or claim territory. In slender anoles (Anolis apletophallus), a small lizard native to Panama, males display a vibrant throat flap called a dewlap during social interactions. Interestingly, some males in this species have an entirely orange dewlap, while others have a mostly white one with just a splash of orange near the base. This difference had long been observed by biologists, but the genetic basis behind it was a mystery.

Our team set out to uncover how this colorful variation is inherited, and what genes might be responsible. To do that, we needed to breed these lizards under controlled conditions—something far easier said than done. Our fieldwork and lab research were based at the Smithsonian Tropical Research Institute (STRI) in the small town of Gamboa, Panama, nestled at the edge of the rainforest. Gamboa is a hub for tropical biology and home to some of the most knowledgeable field researchers I’ve ever met. There, we spent months capturing wild lizards from the same population, which we called “polymorphic” population.

Working in the field came with its own set of challenges. The lizards are quick and often blend perfectly into their leafy surroundings. Days began early and ended late, with hikes through dense forest, traps to check, and detailed records to keep. Despite the heat, humidity, and the occasional run-in with curious monkeys or unexpected snakes, the fieldwork was exhilarating. There’s something incredibly rewarding about holding a tiny, living clue to an evolutionary puzzle in your hand.

Back in the lab facility at STRI in Gamboa, we created 99 breeding crosses between male and female lizards from the different populations. This was one of the most delicate parts of the project—maintaining the right temperature, light cycles, and diet to keep the lizards healthy and reproductive required daily care and a lot of trial and error. Breeding success didn’t always come easy. Sometimes it took weeks for a pair to mate, and hatchlings were raised with careful monitoring to determine which dewlap type they developed.

Once we had enough offspring, we could start to see patterns emerge—and the results were surprising. The inheritance of dewlap color followed a simple Mendelian pattern: the all-orange dewlap (which we call the “solid” morph) was dominant over the orange-and-white “bicolor” morph. For such a striking visual trait, we hadn’t expected the underlying genetics to be so straightforward.

To dig deeper, we used a method called pooled population sequencing (Pool-seq), where we sequenced the DNA of groups of lizards with each dewlap type. This helped us pinpoint genetic regions associated with the trait. Our analysis led us to a promising gene called single-minded 1 (SIM1), which plays roles in color and patterning in other animals. Finding this gene was like discovering the main switch behind the scenes of an evolutionary light show.

This project, with all its logistical hurdles, field adventures, and late-night data sessions, was a reminder of how nature still holds many secrets. Uncovering how such a small animal inherited such a bold trait felt like solving a miniature mystery with big implications. It also opens the door to future research on how genetic variation shapes behavior and appearance in wild animals, and how such traits evolve over time.

Our work is just one piece of a much larger puzzle about how species diversify and adapt in the wild—but it’s a colorful and fascinating piece, and it all started with a few small lizards in the Panamanian rainforest.

Post figure: John David Curlis

Link for the paper: https://rdcu.be/ej4L6