Chromosome-Level Genome Assembly of Five Emberiza Species Reveals the Genomic Characteristics and Intrinsic Drivers of Adaptive Radiation.

Abstract

Emberiza buntings (Aves: Emberizidae) exhibit extensive diversity and rapid diversification within the Old World, particularly in the eastern Palearctic, making them valuable models for studying rapid radiation among sympatric species. Despite their ecological and morphological diversity, there remains a significant gap in understanding the genomic underpinnings driving their rapid speciation. To fill this gap, we assembled high-quality chromosome-level genomes of five representative Emberiza species (E. aureola, E. pusilla, E. rustica, E. rutila and E. spodocephala). Comparative genomic analysis revealed distinct migration-related evolutionary adaptations in their genomes, including variations in lipid metabolism, oxidative stress response, locomotor ability and circadian regulation. These changes may facilitate the rapid occupation of emerging ecological niches and provide opportunities for species diversification. Additionally, these five species exhibited abnormal abundances of long terminal repeat retrotransposons (LTRs), comprising over 20% of their genomes, with insertion times corresponding to their divergence (~2.5 million years ago). The presence of LTRs influenced genome size, chromosomal structure and single-gene expression, suggesting their role in promoting the rapid diversification of Emberiza species. These findings offer valuable insights into the adaptive radiation of Emberiza and establish a robust theoretical foundation for further exploration of the patterns and mechanisms underlying their diversification.