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dc.contributor.authorTesaker, Maria Rundhaugen
dc.date.accessioned2014-05-26T22:00:13Z
dc.date.available2014-05-26T22:00:13Z
dc.date.issued2014
dc.identifier.citationTesaker, Maria Rundhaugen. Male plumage variation and its role in reproductive isolation between house sparrows (Passer domesticus) and Italian sparrows (P. italiae) & A new method for quantifying colours of Passer sparrows using digital imaging in the field. Master thesis, University of Oslo, 2014
dc.identifier.urihttp://hdl.handle.net/10852/39219
dc.description.abstractReproductive barriers between diverging taxa are necessary for speciation to occur. Premating barriers are thought to be of especially great importance, such as plumage colour which is often used in species recognition and mate choice. In this study, I have investigated male plumage variation between a species of hybrid origin, the Italian sparrow (Passer italiae) and one of its parents, the house sparrow (P. domesticus) in their narrow hybrid zone in the Alps. The Italian sparrow is intermediate in plumage between the house sparrow and its other parent, the Spanish sparrow (P. hispaniolensis) but distinctively different from both, hence plumage traits can potentially contribute to premating isolation between the hybrid and its parents. I use cline theory to infer selection on four sexually dimorphic plumage traits in males (crown, cheek, eyebrow and bib). Quantitative measurements of plumage traits were compared with a molecular hybrid index (species-informative SNPs) to compare changes in the plumage traits with genetic changes of a genome-wide average across the hybrid zone. I found crown colour to be under selection, supported by several indirect lines of evidence. The other plumage traits did not seem to be under the same selection pressure, although a significant shift in cheek cline centre was detected, possibly indicating asymmetric female preference in favour of house sparrow cheek colour. Overall, this investigation reveals differential selection pressures among plumage traits across the Alps hybrid zone, where selection against individuals with intermediate crown colour most likely plays a role in premating reproductive isolation in this species complex, thereby contributing to homoploid hybrid speciation. As quantifying bird plumage colours from digital images turned out to be quite challenging in part I of this study, I also developed and improved methods for quantifying such variation when using digital imaging and image analysis. I invented a photo box with a manual flash system and standardized manual settings which constituted a standardized environment, and I implemented the use of a colour standard including a greyscale which allows for later colour correction. Tests comparing light variation between photos in the old and the new method showed that light variation was substantially lower in the new method. Furthermore, new analysis program utilizing the implemented colour standard and exploiting the data in a two-dimensional way, gave the best results in distinguishing colours. Together, the new method and the new analysis in a two-dimensional space yielded data of better quality. Hence, the data retrieved from the new standardized method will be of better quality and allow for more accurate image analysis.eng
dc.language.isoeng
dc.titleMale plumage variation and its role in reproductive isolation between house sparrows (Passer domesticus) and Italian sparrows (P. italiae) & A new method for quantifying colours of Passer sparrows using digital imaging in the fieldeng
dc.typeMaster thesis
dc.date.updated2014-05-27T17:13:18Z
dc.creator.authorTesaker, Maria Rundhaugen
dc.identifier.urnURN:NBN:no-44109
dc.type.documentMasteroppgave
dc.identifier.fulltextFulltext https://www.duo.uio.no/bitstream/handle/10852/39219/1/17-02-13-Tesaker_masteroppgave.pdf


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