Sex− and species−biased gene flow in a spotted eagle hybrid zone

• Main Authors: Väli Ülo, Backström Niclas
• Format: Article
• Language: English
• Published: BMC 2011-04-01
• Series: BMC Evolutionary Biology
• Online Access: http://www.biomedcentral.com/1471-2148/11/100

<p>Abstract</p> <p>Background</p> <p>Recent theoretical and empirical work points toward a significant role for sex-chromosome linked genes in the evolution of traits that induce reproductive isolation and for traits that evolve under influence of sexual selection. Empirical studies including recently diverged (Pleistocene), short-lived avian species pairs with short generation times have found that introgression occurs on the autosomes but not on the Z-chromosome. Here we study genetic differentiation and gene flow in the long-lived greater spotted eagle (<it>Aquila clanga</it>) and lesser spotted eagle (<it>A. pomarina</it>), two species with comparatively long generation times.</p> <p>Results</p> <p>Our data suggest that there is a directional bias in migration rates between hybridizing spotted eagles in eastern Europe. We find that a model including post divergence gene flow fits our data best for both autosomal and Z-chromosome linked loci but, for the Z-chromosome, the rate is reduced in the direction from <it>A. pomarina </it>to <it>A. clanga</it>.</p> <p>Conclusions</p> <p>The fact that some introgression still occurs on the Z-chromosome between these species suggests that the differentiation process is in a more premature phase in our study system than in previously studied avian species pairs and that could be explained by a shorter divergence time and/or a longer average generation time in the spotted eagles. The results are in agreement with field observations and provide further insight into the role of sex-linked loci for the build-up of barriers to gene flow among diverging populations and species.</p>