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A genetic study is rewriting the evolutionary history of the saltwater crocodile and, at the same time, clarifying the species identity of the crocodiles that were exterminated on the Seychelles. The study was published in the journal Royal Society Open Science.
Accounts from early expeditions to the Seychelles more than 250 years ago described crocodiles as common along the coasts of the archipelago. But after the first settlers established a permanent presence in 1770, the Seychelles crocodiles were completely wiped out within 50 years.
A new genetic study now shows that the crocodiles on the remote Seychelles islands did not belong to a separate species. Instead, they represented the westernmost population of the saltwater crocodile (Crocodylus porosus). The result confirms an earlier hypothesis that had been based solely on external characteristics.
In their study, researchers from Germany and the Seychelles examined the evolutionary history and distribution of the saltwater crocodile by comparing its DNA sequences. They combined genetic data from modern samples with mitochondrial genomes from historical museum specimens of the genus Crocodylus, including material from the Seychelles crocodile, which disappeared around 200 years ago.
Among all living crocodiles, the saltwater crocodile is the best adapted to life in the ocean. Special salt glands, for example, allow it to excrete excess salt and survive for long periods in seawater. This enabled the species to colonize islands and coastal regions over thousands of kilometers. “The founders of the Seychelles population must have drifted at least 3,000 kilometers across the Indian Ocean to reach the remote archipelago, perhaps even much further” says reptile expert Frank Glaw of the Bavarian State Collections of Natural History (SNSB) and senior author of the study.
“The genetic patterns suggest that saltwater crocodile populations remained connected over long periods and across great distances, pointing to the high mobility of this species,” explains first author Stefanie Agne of the University of Potsdam. To this day, the saltwater crocodile is one of the most widely distributed reptiles on Earth. Before the Seychelles population was exterminated, its range was even larger, stretching more than 12,000 kilometers from Vanuatu in the Pacific Ocean to the Seychelles in the Indian Ocean.
Dr. Frank Glaw
SNSB - Zoologische Staatssammlung München
E-Mail: glaw@snsb.de
Agne S, Arnold P, Belle B, Straube N, Hofreiter M, Glaw F. 2026 Mitogenomic Crocodylia phylogeny and population structure of Crocodylus porosus including the extinct Seychelles crocodile. R. Soc. Open Sci. 13: 251546. https://doi.org/10.1098/rsos.251546
https://www.snsb.de - Staatliche Naturwissenschaftliche Sammlungen Bayerns (SNSB)
https://zsm.snsb.de - SNSB-Zoologische Staatssammlung München
Saltwater crocodiles can grow to more than six meters in length and weigh over a metric ton. They of ...
Source: Kathrin Glaw
Copyright: SNSB
Sampling the Seychelles crocodiles. The three incomplete skulls from the Seychelles National Museum ...
Source: Kathrin Glaw
Copyright: SNSB
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