Of the smallest monkey in the world, the lion monkey or pygmy marmoset ( Cebuella pygmaea ), which weighs only 100 grams and is approximately the size of a large tomato , there is not just one species – as was believed – but two. A team of scientists from the University of Salford (United Kingdom) has discovered an error in the taxonomy of these creatures that eat insects and that were scientifically described by the German naturalist Johann Spix in early 1823. Their findings have been published in the journal Molecular Phylogenetics and Evolution.
English evolutionary biologists used genome sequencing in numerous specimens of this pygmy marmoset to study its evolutionary history. Their DNA showed that there are actually two separate species of Cebuella that diverged from each other around 2-3 million years ago: one in the north of the Amazon River and one in the south.
Originally from the rainforest of the western Amazon basin, this toy-sized marmoset monkey, its discovery by Johann Spix sparked some controversy in the world of marmoset study.
“ There has been a long confusion about the taxonomy of these wonderful creatures mainly because Spix did not record in his travel diaries the exact location where he collected the type of Cebuella pygmaea in the early 19th century,” explains Jean Boubli, professor of ecology and tropical conservation. and work leader. “That creates confusion about which of the two recently discovered species should keep the original name, the one from the north or the south of the Amazon.”
So these two species have been evolving independently for almost 3 million years, but what is the difference between the two? We have already seen that differentiating them into two different species has been based on genomic evidence, but some differences between species can be observed even with the naked eye. For one thing, north river marmosets tend to be lighter in color and southerners tend to feature darker tinted stripe patterns.
This new discovery could be a game changer for conservationists, as it effectively means that the known population number has dropped by half overnight because the species has suddenly split in two.
Although lion monkeys are a species listed as “Least Concern” on the IUCN (International Union for Conservation of Nature) Red List of Threatened Species, recent disease epidemics have led IUCN’s primate experts to recommend updating that status to “Vulnerable”.
This finding is not in itself strange, since being separated by a river, or any other geographical feature, is a common way by which populations of animals can divide and evolve into two different species. One of the most interesting examples would be the case of chimpanzees and bonobos. These two great apes separated from each other on the evolutionary tree about 2 million years ago as a direct result of the formation of the Congo River in Africa.
Reference: Jean P. Boubli, Maria NF da Silva, Anthony B. Rylands, Stephen D. Nash, Fabrício Bertuol, Mário Nunes, Russell A. Mittermeier, Hazel Byrne, Felipe E. Silva, Fábio Röhe, Iracilda Sampaio, Horacio Schneider, Izeni P. Farias, Tomas Hrbek. How many pygmy marmoset (Cebuella Gray, 1870) species are there? A taxonomic re-appraisal based on new molecular evidence . Molecular Phylogenetics and Evolution , 2018; 120: 170 DOI: 10.1016 / j.ympev.2017.11.010
