Isolation and gene flow in a speciation continuum in newts.

Area of Science:

• Evolutionary Biology
• Genetics
• Speciation Research

Background:

• Reproductive isolation often evolves gradually, allowing gene flow between differentiating lineages.
• Understanding gene flow's role is crucial for comprehending speciation processes.

Purpose of the Study:

• To delimit evolutionary lineages and infer gene flow within the Lissotriton vulgaris species complex.
• To investigate the factors driving genetic differentiation and the impact of gene flow on evolutionary trajectories.

Main Methods:

• Phylogenetic analysis using 74 nuclear markers from 127 localities.
• Integration of diverse methods to delimit evolutionary lineages and infer gene flow.
• Analysis of factors like time since common ancestor and geographic distribution shifts.

Main Results:

• Nine distinct evolutionary lineages were identified in the Lissotriton vulgaris complex.
• Significant post-divergence gene flow was observed, particularly in Central Europe.
• Four southern European lineages (L. graecus, L. kosswigi, L. lantzi, L. schmidtleri) exhibit hallmarks of independent species.
• Widespread mitochondrial DNA (mtDNA) introgression was detected following secondary contact.

Conclusions:

• Distinct newt lineages exchange genes, impacting their evolutionary paths and speciation.
• Genetic differentiation is driven by divergence time and geographic distribution changes.
• Some lineages may achieve complete reproductive isolation, carrying genomic signatures of their complex evolutionary history.