Authors
José Cerca, Ângela M Ribeiro, Michael Matschiner, Rosa Alicia Jiménez, Hugo Pereira, Zheng Oong, Gabriel David, Per Unneberg, Yan Wong, Gabriele Maria Sgarlata, Pim Edelaar, Tomáš Albrecht, Glenn-Peter Saetre, Pedro Cardia, Augusto Faustino, Evandro P Lopes, Rauri C K Bowie, Mark Ravinet, Martim Melo
Published in
Molecular ecology. Volume 35. Issue 21.
Abstract
Ancestral adaptive variation is thought to play an important role in facilitating adaptation to insular environments. However, to properly evaluate its role, we need to determine the age of genetic variation. In this study, we investigate the Iago sparrow (Passer iagoensis), a generalist endemic to the Cabo Verde archipelago, to understand how genetic diversity is maintained in an island lineage where populations are likely ephemeral and adaptation to environmental extremes is ongoing. Using whole-genome sequencing and phenotypic data, we inferred the species' evolutionary history, population structure, and signatures of selection. Our results show that the Iago sparrow diverged from its closest mainland relative approximately 4.26 million years ago, although the colonisation likely occurred only around 2 million years ago. Population structure analyses reveal three distinct lineages, corresponding to geographic divisions within the archipelago, with the Rombos islets population exhibiting significant phenotypic divergence, particularly in bill morphology. Genome scans and phenotypic measurements identified signatures of divergent selection in genes associated with bill size (HMG20B) and bill shape (ALX1), suggesting adaptive evolution in response to local environmental conditions. Our ancestral recombination graph analysis provided temporal estimates for adaptive variation associated with these genes, suggesting that adaptive haplotypes observed in the Rombos population arose after colonisation of the archipelago. This contrasts with patterns described in Darwin's finches, where ancestral variation likely originated prior to colonisation. Our findings highlight the interplay of genetic drift, gene flow, and selection in shaping island species' genetic diversity. The Iago sparrow, a generalist thriving across diverse habitats, provides insights into the mechanisms that maintain genetic diversity in island lineages despite small population sizes and pronounced environmental heterogeneity.
PMID:
42974965
Bibliographic data and abstract were imported from PubMed on 03 Nov 2026.
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