Phylogeographic breaks without geographic barriers to gene flow

Area of Science:

• Population Genetics
• Molecular Ecology
• Biogeography

Background:

• Spatial distribution of genetic markers aids in understanding gene flow and biogeographic history.
• Nonrecombining DNA markers (e.g., mitochondrial DNA, chloroplast DNA) often reveal geographically separated clades meeting at narrow regions.
• Phylogeographic breaks are typically attributed to long-term barriers to gene flow.

Purpose of the Study:

• To investigate the formation of deep phylogeographic breaks within continuously distributed species.
• To determine if phylogeographic breaks can arise without physical barriers to gene flow.
• To explore factors influencing the likelihood of observing phylogeographic breaks.

Main Methods:

• Theoretical modeling of genetic marker spatial distribution and gene genealogies.
• Analysis of factors such as individual dispersal distance and population size.
• Comparison of molecular markers' propensity to show real barriers versus barrier-free breaks.

Main Results:

• Deep phylogeographic breaks can form in continuously distributed species without any barriers to gene flow.
• The probability of observing phylogeographic breaks increases with decreased average individual dispersal distance and population size.
• Molecular markers most sensitive to real geographic barriers are also most likely to reveal breaks formed without barriers.

Conclusions:

• Phylogeographic breaks do not always indicate historical barriers to gene flow.
• Dispersal limitations and population size are key factors in the formation of phylogeographic breaks.
• This finding helps explain discrepancies in phylogeographic breaks observed across different genetic markers or traits within species.