31 May, 2012

More on Buthus phylogeny: Buthus elmoutaouakili in Morocco

My last blog post was about the situation for Buthus phylogeny and taxonomy. Today I learned about another contribution to the knowledge of Buthus in Northern Africa from Martin Husemann and co-workers.

When low dispersal ability of an organism meets geographical barriers, the evolution of inter- and intraspecific differentiation is often facilitated. In the Atlas massif of North Africa, the genus Buthus splits into several species and diverges into numerous genetic lineages, often following the orographic structures of mountain systems. Such high mountain ranges often act as barriers for species with reduced mobility even on small spatial scales. To study the effect of orographic structures on organisms with low dispersal ability, we collected 61 individuals of the scorpion species Buthus elmoutaouakili at 18 locations around the southwestern foothills of the High Atlas and Antiatlas and in the Sousse valley (western Morocco). We analyzed intraspecific differentiation patterns within this geographically restricted area of about 100 x 50 km using 452 bp of the cytochrome oxidase I mitochondrial gene. We detected 5 distinct genetic lineages. In a second analysis, we added 61 previously published sequences from Buthus species from Europe and North Africa. Using a molecular clock approach, we detected old splits (4–5 Ma) separating the samples from 1) the western High Atlas and north of these mountains, 2) the Sousse valley and adjoining mountain areas, and 3) the southwestern Antiatlas. Further differentiation happened in the first 2 geographical groups about 3 Ma. Thus, the divergence time estimates based on a Bayesian approach support the onset of differentiation into these main clades along the Pliocene (5–2.3 Ma) when climatic oscillations started and a constant global cooling preceded the glacial–interglacial cycles of the Pleistocene. Further genetic splits into parapatric groups are detectable for the Sousse valley main group in the early Pleistocene. The climatic oscillations of the Pliocene and early Pleistocene might have caused repeated range shifts, expansions, and retractions leading to repeated vicariance, hereby producing the hierarchical structure of genetic differentiation in B. elmoutaouakili. A taxonomic revision, including morphological and molecular data, is needed to assess the status of each of these Buthus scorpion lineages.

Husemann M, Schmitt T, Stathi I, Habel JC. Evolution and Radiation in the Scorpion Buthus elmoutaouakili Lourenço and Qi 2006 (Scorpiones: Buthidae) at the Foothills of the Atlas Mountains (North Africa). J Hered. 2012;103(2):221-9. [Subscription required for full text]

Thanks to professor Wilson Lourenco for informing me about this article!

Family Buthidae

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