City lizards get their day in the sun

In 1994, a Los Angeles resident vacationed in Taormina, a small coastal town on the coast of Sicily. He returned with seven Italian wall lizards (Podarcis siculus) in his suitcase and released them into his backyard in San Pedro, a neighborhood that’s home to a portion of the bustling Port of Los Angeles.

The small green and brown reptiles thrived in their new environment, according to San Diego State University herpetologist Kinsey Brock.

“And now there are tens of thousands and they're spreading,” she said. “How on earth did seven individuals become tens of thousands?” 

Brock — who joined the SDSU biology department as an assistant professor in January 2024 and also serves as curator of reptiles & amphibians for the SDSU Biodiversity Museum — says the newcomers’ expanding populations are pushing out California’s most common reptile, the Western fence lizard (Sceloporus occidentalis) in parts of Los Angeles and possibly even San Diego. She and her colleagues are investigating whether Italian wall lizards’ long co-existence alongside humans back through antiquity gives them a competitive advantage in their new environs.

“Introductions of this specific species have been studied all over the world because for some reason if they get moved into a city by humans, they establish and they do well.” she said. “Cities in general are known for being these hotspots of invasive species, because humans are moving around cities and traveling, and wildlife hitch rides all the time.”

The researchers are also interested in how the new arrivals fare in places like San Pedro compared to their native Sicily. 

“We know exactly where the guy was on vacation when he took the seven lizards and put them in his suitcase and introduced them to L.A. So we can go back to that population, measure different characteristics that they have, like, what's their preferred temperature? Do they have ectoparasites on their skin? Are they fearful? And we can see how much they've changed and how fast they did it.”

Urban evolutionary biology

As an urban evolutionary biologist, Brock specializes in understanding how urbanization influences the evolution of organisms. In the past, she says many researchers overlooked cities as places to learn about evolution and the natural world. But that view is changing. 

“Historically, people didn't collect many lizard specimens from the city because it wasn't considered “nature,” but reptiles and amphibians and many other organisms besides humans clearly live in cities, and we will be better able to understand how organisms adapt to novel environments and evolve through time if we have historical data on them,” she said. 

As climate change makes California hotter and drier, and cities continue to expand, irrigated cities could provide crucial water resources for wildlife and play an important role in evolutionary change. 

“We usually think of evolution as being this super slow process that takes millions of years to happen and that no human could ever observe. But really, things can happen fast when the environment changes quickly, and if they don't, you don't persist.”

Her team is also interested in how animals adjust their behavior in urban settings, and is finding that Italian wall lizards in San Pedro are relatively fearless compared to their cousins back home in Taormina, Italy. 

“When they're in human-dominated environments, they have a relaxed fear response, but when they're in undeveloped and uninhabited environments, they're very afraid of humans, she said.

Students in Brock’s new lab at SDSU will conduct behavioral experiments to determine whether the relative fearlessness is learned or an evolutionary adaptation. Her lab will also investigate how the newcomers are adapting to Southern California’s microclimate, how they respond to novel predators, and why they’re relatively free of parasites. 

Another project of the Brock lab is to compare the body temperatures and hydration levels of the Western fence lizard living on the bustling SDSU campus with a population of the same species in nearby Mission Trails Regional Park, an open space preserve.

“We’re interested in how urban environments differ in temperature and moisture and how that affects the way lizards are interacting in different environments. Are lizards hotter in cities? Are they more hydrated? How does that affect their behavior? How does that affect their physiology?”

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Island biology

Brock has also spent years comparing the physiology, behavior and morphology of Aegean wall lizards (Podarcis erhardii) — a close relative of Italian wall lizards —  which have co-existed with humans for millennia on different Greek islands. 

She and one of her incoming Ph.D. students will be digging into how interactions with the built landscape have influenced evolutionary changes in the species.

“This is a really cool study system for understanding the speed of evolution in urban environments over long time periods, because humans have been in that landscape, building and urbanizing, for thousands of years,” said Brock. “We can use those islands that have been inhabited by humans for different amounts of time, basically, as different time points in the evolutionary process.”

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Communicating science through art

During her field studies in Greece, Brock is surrounded by art.

“I'm often catching these lizards off of ruins and stone walls,” she said.“When I'm out collecting lizards, a lot of these uninhabited islands have ancient pottery shards around, you find it everywhere in Greece. ”

Brock, who double majored in environmental science and art as an undergraduate at the University of Michigan, often creates art related to her research. For example, the pottery she encountered in Greece inspired her to incorporate lizards into drawings influenced by antiquity. She’s found that art is a way to generate ideas and to communicate about science by getting past the jargon.

“My training as an artist has helped me be a good biologist,” she said. “I think good scientists and artists use their power of observation to connect with people through art or make really cool discoveries in science - both are an attempt to understand the world around us.”

And the parallels don’t end there. 

“In art, you iterate: you make things and then you make them over and over and over again until it's looking the way that you want it to — it’s creative investigation. And that's what a lot of science is: figuring out the appropriate experiment or approach and using technologies and techniques to address big questions in new ways.”

She encourages students whose interest in science and art overlap to pursue both passions. 

“No matter what your identity — artist or whatever — identify how your different way of looking at things brings a uniqueness or a strength to whatever it is you’re doing it and use it.”