An Elevational Phylogeographic Diversity Gradient in Neotropical Birds Is Decoupled from Speciation Rates

Area of Science:

• Evolutionary Biology
• Macroevolution
• Population Genetics

Background:

• Macroevolutionary speciation rates are hypothesized to be influenced by microevolutionary processes.
• Previous research indicates speciation rates increase with elevation in Neotropical birds, but population-level drivers are unclear.

Purpose of the Study:

• To investigate the relationship between elevational phylogeographic diversity and speciation rates in the Andes-Amazonian system.
• To evaluate if population-level genetic differentiation underlies geographical gradients in speciation.

Main Methods:

• Aggregated and georeferenced nearly 7,000 mitochondrial DNA sequences from 103 species/complexes.
• Characterized elevational phylogeographic diversity and population structure metrics.
• Assessed the correlation between population differentiation and speciation rates.

Main Results:

• Increased levels of discrete and continuous population structure were observed in Andean mountains compared to Amazonian lowlands.
• Higher population differentiation did not correlate with higher speciation rates in the studied dataset.
• Decoupling observed between initial population divergence and speciation rates.

Conclusions:

• Geographic gradients in population genetic structure exist between montane and lowland Neotropical birds.
• Population-level differentiation alone does not appear to directly predict macroevolutionary speciation rates.
• Factors like incipient species ephemerality and methodological challenges may explain the observed decoupling.