October 6 : An international team of researchers led by Anna Qvarnstrom at Uppsala University has found in a study of two closely related bird species that the formation of new species is governed by the sex chromosome that the females inherit from their father.

The researchers studied natural hybridisation between the collared flycatcher and the pied flycatcher, the two species that have come into contact with each other after having been separated during the last Ice Age.

It was found that the two bird species could reproduce with each other, but the females were more strongly attracted to a male of their own species.

The researchers say that the gene for this sexual preference is found on the sex chromosome that is inherited from the father. They have also revealed that only female birds have a copy of this chromosome.

“We found that females in the hybrid zone develop a sexual preference for males belonging to their own species and that this preference is determined by genes located on the sex chromosome,” says Anna Qvarnstrom.

The researchers, however, say that the likelihood of the two flycatchers species’ melding into the same species again was very little.

“When genes regulate species-specific features and the preference for these are located close to each other in the DNA, in this case on the same chromosome, species formation is favoured. Therefore, the probability of these two flycatcher species merging into the same species again is small,” says Anna Qvarnstrom.

The study has been published in the online edition of the journal Science. (ANI)