Phylogeography and paleoclimatic range dynamics explain variable outcomes to contact across a species' range

Area of Science:

• Evolutionary Biology
• Ecology
• Genetics

Background:

• Replicability of divergence after contact is poorly understood, especially regarding phylogeography and postglacial range dynamics.
• Understanding how contact zones influence gene flow and speciation is crucial for evolutionary studies.

Purpose of the Study:

• To examine variations in outcomes of contact between divergent lineages of Campanula americana across different contact zone types.
• To investigate gene flow quantity and directionality, phylogeographic structure, and the impact of historical range dynamics on contact zone outcomes.

Main Methods:

• Analysis of contact zones at the leading-, mid-, and rear-edges of the Campanula americana range.
• Assessment of gene flow, admixture, and phylogeographic structure within these contact zones.

Main Results:

• All contact zones formed concurrently through primary contact, but significant admixture was only observed in the rear-edge contact zone.
• Minimal and asymmetric gene flow occurred in the northern leading-edge and mid-range (Virginia) contact zones.
• Strong and symmetric gene flow was detected in the southern rear-edge contact zone, correlating with cytonuclear incompatibility.

Conclusions:

• Speciation processes are highly dependent on existing phylogeographic structure, evolutionary history, and range dynamics.
• Contact zone location significantly influences gene flow patterns and the potential for admixture.
• Asymmetric gene flow in certain contact zones is linked to known cytonuclear incompatibilities.