Genomic architecture underlying morphological and physiological adaptation to high elevation in a songbird

Area of Science:

• Evolutionary biology
• Genomics
• Ecology

Background:

• Organisms adapt to new environments through physiological and morphological changes, leading to adaptive evolution.
• Understanding the genomic basis of adaptation is challenging due to complex ecological factors.
• The rufous-capped babbler (Cyanoderma ruficeps) provides a model for studying adaptation in distinct elevational gradients.

Purpose of the Study:

• To investigate the genomic mechanisms of adaptation in Cyanoderma ruficeps populations across Taiwan's elevational gradients.
• To determine the evolutionary history and colonization routes of Cyanoderma ruficeps in Taiwan.
• To identify genetic factors contributing to morphological and physiological divergence between montane and lowland populations.

Main Methods:

• Genomic sequencing of 43 rufous-capped babblers from five populations.
• Phylogenetic analysis to infer population splits and colonization times.
• Analysis of gene flow and selection signatures between divergent populations.
• Identification of candidate genes and genomic regions associated with altitudinal adaptation.

Main Results:

• The Taiwan Cyanoderma ruficeps lineage diverged from mainland China 1-2 million years ago (Ma) and colonized Taiwan at least twice (0.03–0.22 Ma).
• Montane and lowland populations show divergence with gene flow, indicating strong selection.
• Montane babblers exhibit smaller beaks (COL9A1, SOX11 identified as candidate genes), consistent with Allen's rule.
• Altitudinally divergent mutations are enriched in noncoding regions, chromosomal inversions, and autosomes, potentially regulating genes involved in various physiological and morphological traits.

Conclusions:

• Genomic architecture plays a crucial role in ecological adaptation and population divergence.
• Cyanoderma ruficeps in Taiwan demonstrates adaptation to high-elevation environments (low temperature, hypoxia, high UV).
• The study reveals the genomic underpinnings of morphological and physiological adaptations driven by environmental pressures.