Fine-scale genetic structure and phenotypic divergence of a passerine bird population inhabiting a continuous Mediterranean woodland Garrido Bautista, Jorge Comas Manresa, María del Mar Jowers, Michael Joséph Smith, Steve Penn, Dustin J. Bakkali, Mohammed Moreno Rueda, Gregorio Cyanistes caeruleus Dispersal Genetic structure This work was supported by the project reference PID2022-136400NB-I00 funded by MICIU/AEI/10.13039/501100011033 and by “ERDF/EU”, the projects CGL2014-55969-P and PGC2018-097678-B-I00 (Spanish government), and by a project of the Consejería de Universidad, Investigación e Innovación de la Junta de Andalucía (A-RNM-48-UGR20), all financed with FEDER funds from the European Union (EU). J.G.B. was supported by a FPU pre-doctoral contract from the Spanish Ministry of Education (FPU18/03034), and M.C. was supported by a grant from the Spanish Ministry of Economy and Competitiveness through the Severo Ochoa Programme for Centres of Excellence in Research, Development and Innovation (R+D+I) (SEV-2012-0262), contract number SVP-2014-068620. Genetic differentiation between populations inhabiting ecologically different habitats might appear because of limited dispersal and gene flow, which may lead to patterns of phenotypic divergence and local adaptation. In this study, we use dispersal, genotypic (24 microsatellite loci) and phenotypic (body size and clutch size) data to analyse patterns of genetic structuring and phenotypic divergence in a blue tit (Cyanistes caeruleus) population inhabiting a continuous and heterogeneous woodland along a valley. The two slopes of the valley differ in their forest formations and environmental conditions. Findings showed that most blue tits reproduced within their natal slope. Accordingly, microsatellite analyses revealed that populations of blue tits established in the two slopes show subtle genetic differentiation. The two genetic populations diverged in clutch size, exceeding the level of differentiation expected based on genetic drift, hence suggesting divergent selection (or other processes promoting divergence) on this life-history trait. Our findings reveal that restricted dispersal and spatial heterogeneity may lead to genetic differentiation among bird populations at a surprisingly small scale. In this respect, it is worth highlighting that such differentiation occurs for an organism with high dispersal capacity and within a continuous woodland. Moreover, we show that small-scale ecological differences, together with limited gene flow, can result in selection favouring different phenotypes even within the same continuum population. 2026-01-29T08:05:26Z 2026-01-29T08:05:26Z 2024-05-08 journal article Garrido-Bautista, J., Comas, M., Bakkali, M., Jowers, M. J., Smith, S., Penn, D. J. & Moreno-Rueda, G. (2024). Fine-scale genetic population structure and phenotypic divergence of a passerine bird across a continuous Mediterranean woodland. Royal Society Open Science, 11: 240601. https://doi.org/10.1098/rsos.240601 https://hdl.handle.net/10481/110442 10.1098/rsos.240601 eng http://creativecommons.org/licenses/by-nc-nd/4.0/ open access Attribution-NonCommercial-NoDerivatives 4.0 Internacional Royal Society Publishing