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New species of skink discovered on Socotra Archipelago

23/05/2012 16:21:04

Trachylepis socotrana is present only on Socotra, Darsa and Samha islands, while the skink on Abd Al Kuri island is a newly described species (see Trachylepis cristinae)

Unique biodiversity
May 2012. The Socotra Archipelago, in the north-west Indian Ocean off the coast of Somalia, is considered to be one of the most biodiversity rich group of islands in the world, thanks to a very distinct fauna and flora with a high level of endemicity at both species and generic levels.

UNESCO World Heritage Site
For this reason, it has been designated as UNESCO World Heritage Natural site in 2008. Nevertheless, the natural history of most groups is still not clear, and their origin and evolution remain unknown.

A team of researchers from the Department of Animal Biology (Università di Pavia, Italy), the Institute of Evolutionary Biology (CSIC-UPF, Barcelona, Spain), the Museo Civico di Storia Naturale di Carmagnola (Italy) and the Museum of Science of Trento (Italy), have been investigating the herpetofauna of the archipelago since 2007, in the framework of the ‘Socotra Conservation and Development Project' funded by the Cooperazione Italiana and under the auspices of the United Nations Development Project (UNDP) to collect ecological data on the reptiles of the Socotra Archipelago in order to improve the sustainable development and conservation of the Socotra Archipelago's biodiversity.

In a recent paper, the team presented some new highlights on the systematics, biogeography and evolution of Trachylepis socotrana, the only endemic reptile (a skink) supposed to live in all four islands (Socotra, Darsa, Samha and Abd Al Kuri). By comparing the skinks of the archipelago with representatives of the genus Trachylepis from Middle East, Africa and Madagascar plus some individuals from each of the other three genera of Mabuya skinks sensu lato (Chioninia, Eutropis and Mabuya), they have been able to trace back the history of the Socotran skinks.

Trachylepis cristinae is a newly described species occurring only on Abd Al Kuri island

Trachylepis cristinae is a newly described species occurring only on Abd Al Kuri island

Skink arrived on Socotra twice, 3 million years apart
Interestingly, the results of the phylogenetic analyses indicate that members of the genus Trachylepis arrived in the archipelago in two independent events, firstly colonizing Socotra, Samha and Darsa about 10 million years ago, and then, 3 million years ago, colonizing Abd Al Kuri Island, when all the islands had already drifted away from the mainland.

New species
Furthermore, the Abd Al Kuri skink has proved to be a distinct new species, named by the authors Trachylepis cristinae, to credit the herpetologist who found the holotype while the team was surveying the island. This finding also means that reptiles of Abd Al Kuri, the westernmost island of the archipelago, are, without exception, all endemic to the island.

Once again, the Socotra Archipelago proves to be one of the most unique places in the world to witness and investigate evolutionary processes, and indeed is worthy of its nickname of "Galapagos of the Indian Ocean".

No extinctions in 20th Century
And worthy of similar note, as Kay Van Damme remarks in Nature - Middle East, Socotra has lost none of its unique terrestrial bird, reptile or mollusc species in the last century, contrary to what happened in many other islands in the world. Though, the archipelago is not invulnerable.

Challenges include habitat fragmentation, over-exploitation and loss of traditional knowledge. Tourism, which exponentially increased in recent years, could also be a threat for the most protected -and thus visited- sanctuaries in the islands. But the main concern is nowadays represented by political instability that spreads across Middle East. As Van Damme underlines, political upheavals in Yemen will initiate changes in decision-making on long-term policies and conservation strategies that, in the end, will affect the Socotra Archipelago biodiversity for decades to come.

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