20 May, 2016

What role had the formation of the Andes mountain range on the speciation in the genus Brachistosternus?

The Andes continental mountain chain in South America is one of the worlds longest, and the formation of this mountain chain (The Andean uplift) probably had a major impact of the evolution of plants and animals in this region. The bothriurid genus Brachistosternus Pocock,1893 is endemic to South America and distributed mainly in the Andean region. In a recent article, Sara Ceccarelli and co-workers have investigated the biogeographical history of Brachistosternus to determine the role of Andean uplift on the distribution and diversification of its species.

It is no surprise that this study confirms that the evolution and diversification of Brachistosternus was very much influenced by the major geological changes caused by the Andean uplift.

One of the planet’s most imposing geomorphological features, the Andes, played an important role in the evolution of South America’s flora and fauna. The bothriurid scorpion genus Brachistosternus Pocock, 1893 comprises more than 40 species with high diversity and endemism in the Andes. The present contribution investigates the biogeographical history of this genus using molecular phylogenetics and dating, to determine the role of Andean uplift on the distribution and diversification of its species. 
South America.

A dated species tree was obtained for 55 putative species based on two nuclear and three mitochondrial gene loci. Ancestral ranges and biogeographical events were estimated on the species tree, diversification rates and rate shifts calculated, and areas with high phylogenetic diversity (PD) and evolutionary distinctiveness identified.

Brachistosternus diversified at a steady rate during the main Andean uplift. The central Andean and western slope/Pacific coastal biogeographical provinces played important roles as ancestral areas. Coastal areas of central Chile and southern Peru exhibit high levels of PD in Brachistosternus, suggesting they experienced a relatively long period of ecological stability, while the Andes continued to rise.
Main conclusions 

Andean uplift created new habitats and climate regimes, favouring speciation in genera such as Brachistosternus. Coastal areas to the west of the Andes continued to harbour older lineages while accommodating more recently diverged lineages from the nearby Andes.

Ceccarelli FS, Ojanguren-Affilastro AA, Ramırez MJ, Ochoa JA, Mattoni CI, Prendini L. Andean uplift drives diversification of the bothriurid scorpion genus Brachistosternus. Journal of Biogeography. 2016;Epub 13 May 2016. [Subscription required for full text]

Thanks to Andres Ojanguren-Affilastro for sending me their article!

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