Fitness consequences of hybridization between house sparrows (Passer domesticus) and tree sparrows (P. montanus)
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Gene transfer may occur following hybridization between closely related species if hybrids are viable and able to breed with individuals of one or both of the parental species. House (Passer domesticus) and tree sparrows (P. montanus) occasionally hybridize and produce viable offspring. Previously, we concluded that male tree × house sparrow hybrids are most probably fertile based on the observation of a male F1 hybrid feeding the nestlings with a female house sparrow in two consecutive clutches. However, recent DNA analyses based on blood samples revealed that all nestlings (4) in the first clutch were sired by a neighbouring house sparrow male, whereas nestlings in the second clutch (2) were not blood sampled and most probably died before fledging. This indicates that extensive extra-pair fertilization confounded our previous conclusion, and indicates that social partnership and attending behaviour can be imprecise measures of paternity.
KeywordsDNA-typing Extra-pair fertilizations Hybrids Passerdomesticus Passermontanus
We thank the Ivarsen family for the permission to conduct our studies at their farm at Ytre Kvarøy. The Directorate for Nature Management, the Norwegian University of Science and Technology, the Norwegian Institute for Nature Research and the Norwegian Research Council (Strategic University Programme in Conservation Biology) kindly supported the study financially. This study complies with the current laws of Norway.
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