River barriers and cryptic biodiversity in an evolutionary museum.

Area of Science:

• Ecology
• Evolutionary Biology
• Genetics

Background:

• The Riverine Barriers Hypothesis (RBH) suggests tropical rivers impede gene flow, primarily studied in Amazonian vertebrates.
• Afrotropical avifauna is rich, with many species spanning multiple river basins, yet RBH lacks molecular assessment in this region.
• Understanding riverine barriers is crucial for Afrotropical biodiversity and evolutionary studies.

Purpose of the Study:

• To provide the first molecular evidence of an Afrotropical river acting as a barrier to gene flow in birds and their associated parasites.
• To investigate Pleistocene lineage diversification across the Congo River in four understory bird species and their lice.
• To assess cryptic diversity in Afrotropical forests and its implications for evolutionary history.

Main Methods:

• Genetic analysis of four understory bird species and their lice from north and south of the Congo River.
• Phylogenetic and population genetic analyses to infer lineage divergence and gene flow.
• Comparison of genetic variation patterns between host birds and their parasitic lice.

Main Results:

• The Congo River has acted as a significant barrier to gene flow, leading to near-contemporaneous lineage diversification in birds during the Pleistocene.
• Bird lice exhibit varying genetic variation, correlated with the life-history traits of both hosts and parasites.
• Evidence suggests substantial cryptic diversity in Afrotropical understory birds and their lice.

Conclusions:

• The Congo River functions as an effective barrier to avian and parasitic louse gene flow in the Afrotropics.
• Afrotropical forests have been sites of significant evolutionary diversification throughout the Pleistocene, supporting the Forest Refuge Hypothesis.
• Underestimated biodiversity in the Afrotropics necessitates urgent conservation efforts for these vital forest ecosystems.