Genes drive crows to choose partners that look alike

Crows are all black or grey coated, and they exhibit a strong tendency to select partners that look alike. This behaviour might be rooted in their genetic make-up, a study shows.

The findings showed that it is a likely common evolutionary path that allows for separating populations into novel species.

"Consistent with the hypothesis of colour-mediated isolation, we found that gene expression differed almost exclusively in growing feather follicles at the stage where colour is deposited into the feathers," said researchers from Uppsala University in Sweden.

"Such a mechanism could be common for many other species with visually oriented mate choice," Jochen Wolf from Uppsala University added.

The researchers investigated the genetic architecture of divergence between all black carrion crows and grey coated hooded crows that still hybridise along a hybrid zone stretching across Europe and Asia.

Genes involved in colouration were constitutively expressed higher in black crows than in their grey counterparts.

Screens of more than a billion base pairs in the genome revealed very little difference between the two.

Only 82 base pairs were diagnostically different and 81 of them were concentrated in one genomic region coding for genes involved in colouration and visual perception.

The finding suggest exciting possibilities that a mate-choice relevant trait, like colouration, might be genetically coupled to its perception which could be common one evolutionary path allowing for separating populations into novel species.

The study appeared in the journal Science.