Adnkronos Rome, 11 Feb. (Adnkronos) – New light on the evolution of the Galápagos land iguanas, with previously unpublished details on the timing and mechanisms of their diversification. This is revealed by a study published in the latest issue of Molecular Phylogenetics and Evolution.
By analyzing the DNA of specimens currently living on the Ecuadorian islands, researchers led by Gabriele Gentile, full professor of Zoology at the Department of Biology at the University of Rome Tor Vergata and 'father' of the pink iguana discovered in the early 2000s, have reconstructed the times and methods of their evolution, starting from a common ancestor from the American continent. The study - explains the university in a note - conducted by the International Consortium for Iguanid Reptile Genomes, which involves researchers from the University and other research institutes around the world, confirms that the ancestor of this group of reptiles colonized the archipelago about 10 million years ago, when the current islands had not yet emerged. The lands present at the time, now sunk into the ocean, represented the starting point for a long evolutionary process. The glacial periods of the last hundreds of thousands of years in the Northern Hemisphere have removed water from the oceans, lowering their levels, and have allowed the temporary connection of some of the Galápagos Islands. This has allowed their colonization and the subsequent differentiation of the various species of iguana of the archipelago.
“The research has clarified that the Galápagos pink iguana (Conolophus marthae) originated after the colonization of the island of Isabela, which occurred approximately 500 years ago, much more recently than previously assumed,” explains Gabriele Gentile, coordinator of the international consortium and senior author of the study.
There are various hypotheses regarding the colonization of the Galápagos by the organisms that populate them. A first theory considers the occasional movement from South America of rafts of vegetation, torn from the banks by the floods of the Andean rivers that faced the Pacific coast. These 'islands of vegetation', once captured by what Darwin called the 'Great Equatorial Current', which in about 5 weeks allows a coastal wreck to reach the Galápagos Islands, could have brought new colonizers. Among these, reptiles are certainly the best candidates, since they can resist and endure the period of such a journey in ocean waters. A second theory predicts that from Central America, the animals slowly migrated to the Galápagos thanks to the presence of volcanic islands, now largely disappeared, and favorable ocean currents, different from those of today.
“The demographic analysis highlighted opposite trends in the populations of pink and yellow iguanas (Conolophus subcristatus) that coexist on the Wolf volcano, the highest on the island of Isabela, suggesting a possible competitive interaction between the two species,” adds Cecilia Paradiso, first author of the research, together with Paolo Gratton. “Advances in genomics now allow us to obtain much more precise information from genetic data than in the past,” underlines Gratton. The study of the genetic heritage of the various species of Galápagos iguanas was carried out using the technique called RadSeq, which allowed us to study large portions of the genome in a large number of individuals and provided information on their origin and movements in the past.
Another aspect of the study involved the Santa Fe land iguana (Conolophus pallidus), whose differentiation was determined by geographic isolation due to the rise in ocean levels, which occurred at the end of the last glaciation, which separated the ancestral populations favoring speciation. The study further highlighted how iguana populations have historically been characterized by small size, a factor that could have influenced their genetic diversity and resilience over time. "These results offer new perspectives for the conservation of the archipelago's endemic species, underlining the need for targeted strategies for the protection of this unique biodiversity", the university notes.