1+1=3 - HYBRID SPECIATION IN SPARROWS
In two recent papers by our group, published in Molecular Ecology, the Italian sparrow is shown to be a hybrid species formed by interbreeding between the house sparrow and Spanish sparrow.
The Italian sparrow seems to be aware of its evolutionary history; here in a symbolic split position between two branches (Photo: Ivan Ivanov).
Researchers from the University of Oslo have demonstrated that one of the world’s most common birds is at the centre of an extremely rare event in nature, namely hybrid speciation.
Usually when diverged lineages interbreed, the offspring are infertile or inviable, such as the mule. However, these researchers have shown that the ubiquitous house sparrow (1) has interbred with the Spanish sparrow (+1), forming a third distinct species, the Italian sparrow (=3).
Modes of speciation: bifurcating speciation (left) portrayed by humans and our closest living relatives, and hybrid speciation (right) shown by the case of the Italian sparrow.
Hybrid speciation is an important process, but difficult to observe in nature. Species typically diversify when existing lineages split, creating two species where there was previously one.
Only very rarely does a new and distinct third species arise through the crossing of two extant ones. Therefore, the case of the Italian sparrow provides groundbreaking insight into how new species arise.
The studies have been published in the current issue of Molecular Ecology along with a perspective article highlighting the findings: