African dwarf crocodile is actually three distinct species

December 13th, 2008 - 5:05 pm ICT by ANI  

Washington, Dec 13 (ANI): By looking at the genes of the African dwarf crocodile, scientists have found that the group comprises of three distinct species rather than one.

The analysis was done by a team from the Sackler Institute for Comparative Genomics at the American Museum of Natural History.

This not only ends a long debate about the taxonomy of this group, previously thought to consist of two closely related subspecies, but also defines a new, distinct species from genetic samples.

In the past, the two morphologically distinct crocodile populations were believed to be different genera, then later different species, and then finally different subspecies, explained first-author Mitchell Eaton.

We collected samples in Africa to explore this taxonomic question, and we found a great deal of evolutionary divergence between populations in the Congo Basin and on the west coast of Central Africa. We also, quite unexpectedly, found a completely new species from far West Africa; there may be even more species that we havent sampled yet! he added.

African dwarf crocodiles, genus Osteolaemus, live in the tropical forests of Central and West Africa.

Adults typically grow to no more than 5 feet in length and are the smallest living members of the crocodilian family.

The three groups identified in this current research include a species from the Congo Basin (O. osborni), another from Central Africas Ogooue Basin (O. tetraspis), and the new, yet unnamed species from West Africa.

All of these crocodiles look very similar, and all are widely hunted by local people as a source of food.

In the laboratory, the researchers sequenced more than 4,000 base pairs of both mitochondrial and nuclear DNA from as many as 82 individuals sampled across Central and West Africa.

The results confirmed species-level separations between three different groups of dwarf crocodiles.

Crocodiles from the Congo Basin appear to be the oldest of the three species, with some morphological characteristics placing them closer to a shared ancestor of the Nile crocodile.

The dwarf crocodiles of the Ogooue and West Africa, on the other hand, are more recently evolved and are more closely related to each other than either is to the Congo Basin species.

These species have been on their own evolutionary trajectory for a long time, said George Amato, Director of the Sackler Institute.

They are diagnostically distinctevery individual in one species has characteristics that are not found in the other species, and the number of diagnostic characteristics is large, he added. (ANI)

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