Rugged relief and climate promote isolation and divergence between two neotropical cold-associated birds

Area of Science:

• Ecology and Evolutionary Biology
• Bioinformatics and Computational Biology
• Neotropical Biogeography

Background:

• Tropical mountain diversity is shaped by historical factors, including climate fluctuations and complex topography.
• Understanding diversification dynamics requires explicit spatio-temporal analyses of range shifts and their genomic impact.
• Previous studies highlight climate-topography interactions but lack detailed temporal frameworks.

Purpose of the Study:

• To investigate the evolutionary history of two warbling finch species (genus Microspingus) in the Montane Atlantic Forest.
• To test the role of climate and topography in shaping diversification patterns using niche modeling and population genomics.
• To elucidate historical range shifts and their consequences on genetic structure and gene flow.

Main Methods:

• Utilized niche modeling to predict species distributions over the last 800,000 years.
• Employed subgenomic population-level datasets to infer population structure and demographic history.
• Conducted demographic simulations to test hypotheses of isolation, population size stability, and gene flow.

Main Results:

• Identified three genetically distinct populations of warbling finches, congruent with geographic and phenotypic variation.
• Demographic simulations indicated asynchronous population isolation around 40,000 years ago, with stable sizes and past gene flow.
• Niche models revealed cyclical range expansions into lowlands during glacial periods and contractions to higher altitudes during interglacials, consistent with observed introgression.

Conclusions:

• Cyclical climate changes play a dual role: promoting divergence and persistence in mountains during warm periods, and expansion/admixture in lowlands during cold periods.
• The interplay between landscape complexity and climate is a crucial mechanism driving Neotropical montane biota evolution.
• Findings provide a spatio-temporal framework for understanding diversification in response to past climate dynamics.