Rapid ecological specialization despite constant population sizes

Area of Science:

• Genetics
• Evolutionary Biology
• Zoology

Background:

• The bushbuck (Tragelaphus scriptus) is a diverse ungulate species complex.
• Recent studies reveal two genetically divergent lineages: Scriptus (north-west Africa) and Sylvaticus (south-east Africa).
• These lineages are paraphyletic at mtDNA due to ancient hybridization.

Purpose of the Study:

• To test hypotheses of historical demography and adaptation in bushbuck.
• To utilize a higher-resolution genetic framework with nuclear and mitochondrial markers.
• To clarify the evolutionary history and relationships between bushbuck lineages.

Main Methods:

• Reconstructed genealogies using four nuclear (MGF, PRKCI, SPTBN, THY) and three mitochondrial markers.
• Inferred demographic history using coalescent-based methods.
• Conducted phylogeographic and dispersal-vicariance analyses on nuclear DNA.

Main Results:

• Confirmed two divergent Scriptus and Sylvaticus lineages using both nuclear and mtDNA.
• Dated the common ancestor of the two lineages to approximately 2.54 million years ago.
• Showed bushbuck originated in East Africa, with Scriptus colonizing west and Sylvaticus radiating south, primarily via vicariance events.

Conclusions:

• Confirmed independent evolution of Menelik's bushbuck, supporting convergent evolution.
• Both lineages exhibited stable population sizes throughout the Pleistocene, a period of significant African environmental change.
• The findings highlight remarkable demographic stability despite major climatic and tectonic shifts.