In a groundbreaking study, researchers in South Florida have observed an extraordinary event that offers unprecedented insight into the forces of evolution as two Caribbean lizard species came face to face for the first time. This remarkable interaction is providing vital evidence of natural selection and character displacement—the process by which similar species adapt when competing for the same resources.

James Stroud, an assistant professor at the School of Biological Sciences, was initially focused on studying the Cuban brown anole (Anolis sagrei) at the Fairchild Tropical Botanic Garden when the Puerto Rican crested anole (Anolis cristatellus) unexpectedly invaded their habitat in 2018. The subsequent competition between these two closely related lizards has become a precious case for understanding evolutionary dynamics.

The findings, recently published in *Nature Communications*, show the remarkable changes that occurred when both species began to vie for limited resources. "Most of the knowledge we have about these evolutionary responses comes from historical data. This instance allowed us to watch evolution unfold in real-time," Stroud explained, emphasizing the rarity of such opportunities.

A Clash of Titans: Similarities and Divergence

Despite having been separated by about 40 to 60 million years of evolution on different Caribbean islands, the Cuban brown anole and the Puerto Rican crested anole occupy nearly identical ecological niches—creating an intense competition for food and territory once the latter arrived.

Stroud's team had a significant head start in their research, having monitored the Cuban brown anole’s behavior prior to the crested anole's appearance. This gave them the unique advantage of observing real-time changes as these lizards adapted to their new rivals. They meticulously analyzed their changing diets, habitats, and movements, measuring over 1,000 lizards to track shifts in their perch heights—the key indicator of habitat division among Anolis lizards.

Survival of the Fittest: Adapting to Thrive

The researchers discovered that the Cuban brown anoles began to spend more time on the ground and evolved longer legs, which facilitated faster movement in this niche. Meanwhile, the Puerto Rican crested anole adapted to life in higher vegetation. "Lizards with longer legs exhibited better survival rates when the crested anoles arrived, mirroring traits seen in populations that have coexisted for generations," Stroud noted.

This research not only sheds light on the complex processes of evolution but also highlights how human activities—like habitat modification—create scenarios for these natural experiments. Intriguingly, both species were introduced to South Florida by humans, underscoring the significant impact of anthropogenic factors on ecological systems.

What Lies Ahead: Predicting Evolutionary Outcomes

As species increasingly intermingle due to globalization and climate change, studies like this may hold the key to understanding how ecological communities respond to such challenges. Observing these non-native lizards—seeing them interact for the very first time—has offered scientists a rare glimpse into evolutionary processes at work.

"This unique situation enables us to connect observed evolutionary patterns with real-time changes, thus enriching our understanding of natural selection," Stroud concluded. The implications of this research reach far beyond the lizards of South Florida—potentially informing conservation efforts and management strategies in a rapidly changing world.

Stay tuned, as this thrilling tale of evolution continues to unfold!