North African hybrid sparrows (Passer domesticus, P. hispaniolensis) back from oblivion – ecological segregation and asymmetric mitochondrial introgression between parental species

摘要

A stabilized hybrid form of the house sparrow (Passer domesticus) and the\udSpanish sparrow (P. hispaniolensis) is known as Passer italiae from the Italian\udPeninsula and a few Mediterranean islands. The growing attention for the Italian\udhybrid sparrow and increasing knowledge on its biology and genetic constitution\udgreatly contrast the complete lack of knowledge of the long-known\udphenotypical hybrid sparrow populations from North Africa. Our study provides\udnew data on the breeding biology and variation of mitochondrial DNA in\udthree Algerian populations of house sparrows, Spanish sparrows, and phenotypical\udhybrids. In two field seasons, the two species occupied different breeding\udhabitats: Spanish sparrows were only found in rural areas outside the cities and\udbred in open-cup nests built in large jujube bushes. In contrast, house sparrows\udbred only in the town centers and occupied nesting holes in walls of buildings.\udPhenotypical hybrids were always associated with house sparrow populations.\udHouse sparrows and phenotypical hybrids started breeding mid of March, and\udmost pairs had three successive clutches, whereas Spanish sparrows started\udbreeding almost one month later and had only two successive clutches. Mitochondrial\udintrogression is strongly asymmetric because about 75% of the rural\udSpanish sparrow population carried house sparrow haplotypes. In contrast,\udpopulations of the Italian hybrid form, P. italiae, were genetically least diverse\udamong all study populations and showed a near-fixation of house sparrow haplotypes\udthat elsewhere were extremely rare or that were even unique for the Italian\udPeninsula. Such differences between mitochondrial gene pools of Italian and\udNorth African hybrid sparrow populations provide first evidence that different\uddemographic histories have shaped the extant genetic diversity observed on\udboth continents.