Genomic variation, population history and within-archipelago adaptation between island bird populations

Oceanic island archipelagos provide excellent models to understand evolutionary processes. Colonization events and gene flow can interact with selection to shape genetic variation at different spatial scales. Landscape-scale variation in biotic and abiotic factors may drive fine-scale selection within islands, while long-term evolutionary processes may drive divergence between distantly related populations. Here, we examine patterns of population history and selection between recently diverged populations of the Berthelot's pipit (Anthus herthelotii), a passerine endemic to three North Atlantic archipelagos. First, we use demographic trees and h statistics to show that genome-wide divergence across the species range is largely shaped by colonization and bottlenecks, with evidence of very weak gene flow between populations. Then, using a genome scan approach, we identify signatures of divergent selection within archipelagos at single nucleotide polymorphisms (SNPs) in genes potentially associated with craniofacial development and DNA repair. We did not detect within-archipelago selection at the same SLAPS as \,v ere detected previously at broader Spati al scales between archipelagos, hut did identify signatures of selection at loci associated with similar biological functions. These findings suggest that similar ecological factors may repeatedly drive selection between recently separated populations, as well as at broad spatial scales across varied landscapes.

Automated summary

Oceanic island archipelagos offer valuable insights into evolutionary processes, with interactions between colonization events, gene flow, and selection shaping genetic variation at different spatial scales. Within the same geographical region, similar ecological factors may repeatedly drive selection between populations.