Cross dressing among humans may imply that a person wants to attract the same sex. In male wading birds, however, cross dressing is a strategy to get the attention of female birds and hopefully a mating partner.
In a new genome-sequencing study, researchers were able to discover that a so-called "supergene" can explain the diverse and bizarre strategies that wading birds practice in order to steal mates.
In 1995, the researchers found that the various courting approaches of male ruffs (Philomachus pugnax) were driven by a single inherited factor. However, experts found it hard to believe that a whole range of behavioral and physical characteristics could be triggered by only one gene.
A supergene, which contains about 4.5 million DNA letters and comprised of 125 individual genes, appears to be responsible as explained in a report led by Terry Burke from University of Sheffield and Leif Andersson from Uppsala University in Sweden.
Normally, a long and continuous DNA would eventually break down and mix maternal and paternal chromosome sections that develop in each generation. About 3.8 million years ago, a long stretch of DNA inverted itself and the ruff's supergene was created. The inversion halted genes contained inside to recombine with genes on a sister chromosome.
About 500,000 years ago, a new version of inversion transpired, restoring the DNA stretch to its original sequence, building a second version.
Three types of birds emerged following the generations of DNA changes. The difference between these types is the presence or absence of gene copies in the first and second inversions.
Independent male birds lack both forms of the inversion. Boasting black and brown neck feathers, these birds are considered territorial and defensive on the breeding ground.
Satellite male birds have one copy of the second inversion gene. These white-feathered birds invade independent males to steal females.
Lastly, the faeders, which have one copy of the first inversion gene, resemble females and use this striking feature to disrupt coital encounters.
Fredrik Widemo, one of the study authors, explained that while independents and satellites are benefited from interaction with female ruffs, faeders may also have its chance at mating females when other males are engrossed in interaction within its gender circle.
"It's nice example of how evolution can throw up spectacular things on very rare occasions," said Burke.
The study was published in the journal Nature Genetics on Monday, Nov 16.
