Scientists led by Dr Kristofer Helgen from the Smithsonian Institution’s National Museum of Natural History have erected a new genus called Neomonachus for two species of monk seals: the recently extinct Caribbean monk seal and the extant but critically endangered Hawaiian monk seal. This discovery is the first time in more than 140 years that a new genus has been recognized amongst modern pinnipeds (seals, sea lions, and walruses).
This is an artist’s impression of the recently extinct Caribbean monk seal. Image credit: Peter Schouten.
The now-extinct Caribbean monk seal (Monachus tropicalis), also known as sea-wolf, was one of three species of monk seal in the world.
It was first reported by Columbus in 1494 and ranged throughout the Caribbean with an estimated population in the hundreds of thousands.
Unrestricted hunting in the 19th century, however, caused a rapid decline in numbers. The last sighting of a Caribbean monk seal was in 1952, making it the most recent extinction of a marine mammal in the Western Hemisphere.
The other two species are the Hawaiian monk seal (Monachus schauinslandi) and the Mediterranean monk seal (Monachus monachus). Both are listed as critically endangered by IUCN, with about 1,200 Hawaiian and less than 600 Mediterranean monk seals left.
The relationship between these three species has never been fully understood.
To find the answer, Dr Helgen and his colleagues turned to DNA extracted from century-old monk seal skins in the collections of Smithsonian Institution.
Their analysis, published in the open-access journal ZooKeys, shows that the Caribbean species was more closely related to the Hawaiian rather than the Mediterranean monk seal.
It also shows that Caribbean and Hawaiian monk seals split into distinct species around 3 to 4 million years ago – the same time the Panamanian Isthmus closed off the connection between the Atlantic and Pacific Oceans, which would have naturally separated the two.
According to the scientists, the molecular and morphological differences between the Mediterranean species and the two New World species (Caribbean and Hawaiian) are profound. This led them to classify the Caribbean and Hawaiian monk seals in a new genus, Neomonachus.
“Scientists have long understood that monk seals are very special animals. This study is exciting because it gives us a clearer view of their evolution and provides us with new context that highlights the importance of conserving these remarkable and endangered seals,” Dr Helgen concluded.
______
Martin-Scheel D et al. 2014. Biogeography and taxonomy of extinct and endangered monk seals illuminated by ancient DNA and skull morphology. ZooKeys 409: 1–33; doi: 10.3897/zookeys.409.6244
