BRANTA — Keith W. Larson
Hybrid zone dynamics, assortative mating, and migratory programmes in a willow warbler migratory divide
Institution: Lund University, Sweden
Supervisors: Susanne ├àkesson, Staffan Bensch
Details: PhD 2012 (Completed)
Subject Keywords: migratory divide, phenotype, willow warbler, hybrid zone, tension zone, Phylloscopus trochilus, migratype, assortative mating, migration
Species Keywords: willow warbler, Phylloscopus trochilus
Thesis online at http://lup.lub.lu.se/refmole/detail/3046745
In this thesis I will present and contrast the two willow warbler subspecies (Phylloscopus trochilus trochilus and P. t. acredula) or migratory phenotypes in the context of their migratory divide and hybrid zone in central Sweden. In the first paper I investigate the role of population abundance in determining the location of the hybrid zone. Specifically, is there a region of low abundance associated with the hybrid zone? Further, is the hybrid zone located on an environmental gradient which might suggest that breeding ground environmental conditions are responsible for the lower abundance? This lower abundance may reflect the unsuitability of habitats along the environmental gradient for either parental or hybrid offspring. In my second paper, I ask if there are population specific differences in their wintering moult ecology that can be elucidated from diet derived stable isotope patterns in their winter moulted primary flight feathers? The third paper addresses the important question, does assortative mating lead to reproductive isolation or do these very similar subspecies hybridize and produce offspring? In my fourth paper, I ask does local adaptation to environmental conditions, such as temperature extremes and the short growing season, in mountain populations of willow warblers explain the apparent distribution of the 'northern-allele- for the AFLP derived genetic marker WW1? Finally, in the fifth paper, I conduct a detailed analysis of phenotypic traits at 50 sites across the hybrid zone, including 35 sites visited more than once. Here I ask, does lower abundances in the west of the hybrid zone predict the zone to be wider in the west than in the east? Further, using data from repeated visits to sites across the zone, we predict low repeatabilities for migratory associated traits that would suggest that high annual turn-over in migratory phenotypes occupying the zone. To better understand the hybrid zone dynamics it will be essential to develop genetic markers that allow one to separate each parental migratype, hybrids, and backcrosses. Once markers allow the identification of hybrid offspring, orientation experiments should be conducted to elucidate migratory directional preferences that would support our hypothesis that hybrids take an intermediate migratory direction to their parental migratypes.
Larson, K. W., Liedvogel, M., Addison, B., Kleven, O., Laskemoen, T., Lifjeld, J. T., Lundberg, M., ├àkesson, S. & Bensch, S. 2014. Allelic Variation in a Willow Warbler Genomic Region Is Associated with Climate Clines. PLoS ONE 9:e95252. DOI: 10.1371/journal.pone.0095252.
Larson, K. W., Liedvogel, M., Bensch, S., ├àkesson, S., Wassenaar, L. I. & Hobson, K. A. 2013. Inferring the ecology of willow warblers during their winter moult by sequential stable isotope analyses of remiges. Journal of Avian Biology 44: 561-566. DOI: 10.1111/j.1600-048X.2013.00050.x.
Miriam L., Larson, K. W., Lundberg, M. Gursoy, A., Wassenaar, L. I, Hobson, K. A., Bensch, S. & ├àkesson, S. 2014. No evidence for assortative mating within a willow warbler migratory divide. Frontiers in Zoology (accepted).