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The Remarkable Journey of Fijian Iguanas

In a fascinating chapter of evolutionary history, a remarkable event occurred millions of years ago when a group of adventurous iguanas crossed the vast Pacific Ocean, reaching the remote islands of Fiji on makeshift rafts made of vegetation.

The origin of iguanas in Fiji and Tonga has long intrigued scientists. Although iguanas are primarily native to the Americas and the Caribbean, evidence suggests a small group somehow traversed the ocean to arrive in Fiji—a feat made all the more perplexing by the absence of any land bridge connecting these distant locations. This raises the question: how did they manage such a daunting journey?

According to Simon Scarpetta, an evolutionary biologist at the University of San Francisco, and his research team, the mystery may have been unraveled. They propose that these iguanas hitched a ride on natural rafts of trees, plants, or other floating debris that occasionally break away from coastlines and drift across the sea. Such “floating islands” can transport animals to far-flung lands, and in the case of Fijian iguanas, researchers estimate they undertook an unprecedented journey of over 8,000 kilometers across the Pacific.

Scarpetta elaborated on this idea, suggesting a scenario where a cyclone might have uprooted trees—carrying iguanas and their eggs along with them—after which they could have utilized ocean currents to navigate their way across the water. Such an event would have created the perfect opportunity for these reptiles to embark on their epic voyage.

Adaptability and Resilience

For vertebrates, surviving such extensive oceanic travels is notably rare. Yet iguanas possess unique adaptations that could facilitate endurance during prolonged deprivation of food and fresh water. Known for their ability to survive for weeks without sustenance, iguanas are equipped for such arduous expeditions. Previous observations have indicated their capacity to raft, with a notable instance in 1995 when a group of approximately 15 iguanas was seen traveling 320 kilometers between Caribbean islands on debris created by a hurricane. Researchers speculate that the iguanas’ slow metabolism and the collection of rainwater played pivotal roles in their survival on the lengthy journey to Fiji.

Historically, two primary theories have attempted to explain the presence of these iguanas in Fiji. One posits that they rafted from the Americas, while the second suggests they may have descended from an extinct ancestor that drifted from either Asia or Australia.

To shed light on their evolutionary background, Scarpetta and his team examined over 200 species of iguanas and lizards. Their findings reveal that the four iguana species native to Fiji are most closely related to the desert iguanas found in Mexico and the American Southwest, indicating a clear lineage. However, the timeline for this significant voyage into the Pacific remains ambiguous.

Scarpetta notes, “This suggests that as soon as land appeared where Fiji now exists, these iguanas may have colonized it. Regardless of the precise timing of this dispersal, the event itself is nothing short of extraordinary.”

Source
explorersweb.com