Gene Flow Complicates Phylogenetic Inference in an Archipelago Radiation

Area of Science:

• Evolutionary Biology
• Biogeography
• Population Genetics

Background:

• Allopatric divergence is key to biogeography and community assembly.
• Gene flow between isolated populations affects adaptation, speciation, and phylogenetic inference.
• Superspecies offer insights into gene flow's impact on divergence.

Purpose of the Study:

• Investigate gene flow, population structure, and phylogenetic relationships in the Solomons Monarchs avian superspecies.
• Characterize the effects of geographic barriers and gene flow on divergence.
• Address challenges in phylogeographic inference when populations are differentially isolated.

Main Methods:

• Phylogenetic analyses of the Symposiachrus barbatus complex.
• Population genetic simulations.
• Analysis of gene flow patterns influenced by geographic barriers.

Main Results:

• Gene flow among allopatric Solomons Monarchs aligns with geographic predictions.
• Phylogenetic relationships contradict a simple stepping-stone colonization model.
• An isolated island's species appeared sister to all others, challenging colonization history inference.

Conclusions:

• Low gene flow in isolated populations can bias phylogenetic inference.
• Distinguishing gene flow from colonization history is a significant challenge in phylogeography.
• Geographic isolation complicates understanding evolutionary divergence and speciation.