Abstract
A stabilized hybrid form of the house sparrow (Passer domesticus) and the Spanish sparrow (P. hispaniolensis) is known as Passer italiae from the Italian Peninsula and a few Mediterranean islands. The growing attention for the Italian hybrid sparrow and increasing knowledge on its biology and genetic constitution greatly contrast the complete lack of knowledge of the long‐known phenotypical hybrid sparrow populations from North Africa. Our study provides new data on the breeding biology and variation of mitochondrial DNA in three Algerian populations of house sparrows, Spanish sparrows, and phenotypical hybrids. In two field seasons, the two species occupied different breeding habitats: Spanish sparrows were only found in rural areas outside the cities and bred in open‐cup nests built in large jujube bushes. In contrast, house sparrows bred only in the town centers and occupied nesting holes in walls of buildings. Phenotypical hybrids were always associated with house sparrow populations. House sparrows and phenotypical hybrids started breeding mid of March, and most pairs had three successive clutches, whereas Spanish sparrows started breeding almost one month later and had only two successive clutches. Mitochondrial introgression is strongly asymmetric because about 75% of the rural Spanish sparrow population carried house sparrow haplotypes. In contrast, populations of the Italian hybrid form, P. italiae, were genetically least diverse among all study populations and showed a near‐fixation of house sparrow haplotypes that elsewhere were extremely rare or that were even unique for the Italian Peninsula. Such differences between mitochondrial gene pools of Italian and North African hybrid sparrow populations provide first evidence that different demographic histories have shaped the extant genetic diversity observed on both continents.
Highlights
Hybridization has been considered as the driving force of speciation in several groups of organisms
Such differences between mitochondrial gene pools of Italian and North African hybrid sparrow populations provide first evidence that different demographic histories have shaped the extant genetic diversity observed on both continents
The two urban Algerian populations of Djelfa and Hassi El-Euch were constituted by house sparrows, and phenotypical hybrid sparrows were exclusively associated with that species (“mixed urban populations” hereafter)
Summary
Hybridization has been considered as the driving force of speciation in several groups of organisms (review in: Abbot et al 2013). Hybridization processes were most intensely studied in the context of a breakdown of reproductive barriers in secondary contact rather than with respect to the emergence of truly stabilized hybrid species. A great number of narrow-range avian hybrid zones have been circumscribed in the Palearctic, but in most areas, distribution range of hybrids is limited to rather narrow zones of secondary contact in coexistence with both parental species (Haffer 1989; Aliabadian et al 2005). Ecology and Evolution published by John Wiley & Sons Ltd. Ecology and Evolution published by John Wiley & Sons Ltd
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