'Supergene' Determines Male Ruff Birds' Mating Strategy

Male ruffs, a Eurasian species of shorebirds, have a particularly interesting mating behavior – a practice known as lekking. In this, they gather in groups to attract females by sporting diversely colored feathers that are the expressions of distinctive genomes--signalling whether they are the kind of mate that is territorial, a girlfriend stealer or a "cross dresser."

In a recent study, researchers from the University of Sheffield took a closer look at differences observed among the three male types during spring mating season. Researchers found that males with spectacular neck and head feathers are territorial by nature, while those with white feathers were observed to steal mates from other males. Scientists labelled the third bird type "cross-dressers" because their feathers mimic those of the females they are trying to attract.

Such expressions can be traced to several million years ago, to a "supergene" that evolved due to a chromosomal rearrangement that occupies a section of a chromosome containing a hundred or more genes.

"The special feature of the supergene is that it allows lots of genes that are next to each other on a chromosome – which, in this case, determine multiple traits including hormones, feathering, color and size – to evolve together and create two distinct behavioral traits," Professor Terry Burke, lead author from the University's Department of Animal and Plant Sciences, said in the university's news release.

Essentially, when the gene originated it allowed female mimics to evolve and coexist with territorial males.

"This process is similar to the one that led to the evolution of separate sex chromosomes, and indeed the alternative forms of the supergene combined together to create the third type of bird personality – the girlfriend stealer," Burke added. "Unlike young men at a social occasion who have each chosen a different approach to courtship, whether that's showing off or paying a compliment, for these birds there is no choice in the matter. It's their DNA that dictates how they win a partner."

This study, recently published in the journal Nature Genetics, sheds light on how even the slightest genetic changes can lead to fundamental differences in attractiveness and behavior.

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