Population differentiation and restricted gene flow in Spanish crossbills: not isolation‐by‐distance but isolation‐by‐ecology

• Published in: Journal of evolutionary biology Vol. 25; no. 3; pp. 417 - 430
• Main Authors: EDELAAR, P., ALONSO, D., LAGERVELD, S., SENAR, J. C., BJÖRKLUND, M.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01-03-2012
• Subjects: Adaptation; Adaptation, Biological - genetics; Adaptations; Analysis of Variance; Animals; Base Sequence; Beak - anatomy & histology; Birds; divergent selection; DNA, Mitochondrial - genetics; ecological speciation; Ecosystem; Evolutionary biology; Gene flow; Gene Flow - genetics; Genetic Variation - genetics; Genetics, Population; Geography; landscape genetics; Loxia curvirostra; Mitochondrial DNA; Molecular Sequence Data; Morphology; Neutral gene; Passeriformes - anatomy & histology; Passeriformes - genetics; Passeriformes - physiology; Phenotype; Population differentiation; population divergence; Population Dynamics; Population genetics; Population structure; reproductive isolation; resource specialization; Selection, Genetic; Sequence Analysis, DNA; Spain; Speciation; Vocalization, Animal - physiology; Spain
• ISSN: 1010-061X; 1420-9101; 1420-9101
• DOI: 10.1111/j.1420-9101.2011.02443.x

Divergent selection stemming from environmental variation may induce local adaptation and ecological speciation whereas gene flow might have a homogenizing effect. Gene flow among populations using different environments can be reduced by geographical distance (isolation‐by‐distance) or by divergent selection stemming from resource use (isolation‐by‐ecology). We tested for and encountered phenotypic and genetic divergence among Spanish crossbills utilizing different species of co‐occurring pine trees as their food resource. Morphological, vocal and mtDNA divergence were not correlated with geographical distance, but they were correlated with differences in resource use. Resource diversity has now been found to repeatedly predict crossbill diversity. However, when resource use is not 100% differentiated, additional characters (morphological, vocal, genetic) must be used to uncover and validate hidden population structure. In general, this confirms that ecology drives adaptive divergence and limits neutral gene flow as the first steps towards ecological speciation, unprevented by a high potential for gene flow.