New Insights into the Journey of Fijian Iguanas from North America
Recent genetic research reveals that Fiji’s iguanas are closely related to lizards from North America’s deserts, shedding light on their incredible migration.
Distinctive with their vibrant green scales and unique powder blue and white markings, Fijian iguanas are emblematic of the lush tropical landscapes of Fiji. However, the origin of these remarkable lizards has baffled scientists for years.
Recent genetic analysis supports a fascinating theory: these iguanas migrated from the deserts of southwestern North America, covering an astonishing distance of over 5,000 miles in what is considered one of nature’s greatest oceanic migrations.
While iguanas are known to inhabit islands across the Caribbean and the Galápagos, their journey to Fiji, situated more than 1,600 miles east of Australia, stands out among these travels.
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Previous theories suggested that iguanas could have reached Fiji via land bridges formed during the break-up of the southern supercontinent Gondwana or by floating on natural rafts made of vegetation from South America, a journey that would take months. However, this new research highlights a different scenario.
By analyzing the genomes of Fijian iguanas and comparing them to those of several species in the Americas, the study found that Fijian iguanas are most closely related to desert iguanas in the genus Dipsosaurus, indicating their lengthy separation from their North American relatives.
Desert Iguana (Dipsosaurus dorsalis).
The connection between the endangered Fijian iguanas and their desert counterparts surprised many biologists. Evolutionary biologists noted that they expected a common ancestor with other iguana species, but instead were met with unexpected findings. This highlights the complexity and unpredictability of evolutionary pathways.
According to researchers, Fijian iguanas diverged from their North American relatives between 34 and 31 million years ago, which aligns with the rafting hypothesis. Their unprecedented journey likely involved floating on debris mats carried across vast ocean expanses, marking it as the longest oceanic dispersal recorded for any terrestrial vertebrate.
Study co-author Simon Scarpetta pointed out that iguanas’ physiological traits, including resilience to heat and starvation due to their slow metabolism, make them perfectly suited for such long journeys. “They are an ideal group of vertebrates to survive an extensive rafting event over open ocean,” he stated.
