90-Gene Cluster Key to Divergent Plumage & Spectacular Mating Behavior in Eurasian Shorebird Males; Causative Balanced Polymorphism Has Been Maintained for 4 Million Years; Cluster Contains Genes for Sex Hormone Regulation and Pigmentation

The ruff is a Eurasian shorebird that has a spectacular “lekking” behavior (a typer of mating behavior), in which highly ornamented males compete for females. Now, two independent research groups report that male ruffs with alternative reproductive strategies carry a chromosomal rearrangement that has been maintained as a balanced genetic polymorphism for approximately 4 million years. [Note: “Lekking” is a mating ritual in some species, in which males assemble on the mating ground (the lek), where they spar with each other or put on extravagant visual or aural displays (mating dances or gymnastics, plumage displays, vocal challenges, etc.) so that a female will select them for mating. The two studies, one led by scientists at Uppsala University in Sweden, and the other led by scientists at the UK’s University of Sheffield and at the Univesrsity of Graz in Austria, were published online on November 16, 2015 in Nature Genetics. The Uppsala article is titled “Structural Genomic Changes Underlie Alternative Reproductive Strategies in the Ruff (Philomachus pugnax).” The UK/Austria study is titled “A Supergene Determines Highly Divergent Male Reproductive Morphs in the Ruff.” Three different types of ruff males are seen at the “leks” (mating grouns) of this species (see accompanying video, link below). “Independent” males show colorful ruffs and head tufts and fight vigorously for territories. “Satellite” males are slightly smaller than “Independents,” do not defend territories, and have white ruffs and head tufts. “Faeder” males mimic females by their small size and lack of ornamental feathers, and they do not defend territory. The “Independent” and “Satellite” males show a remarkable interaction in which the “Satellite” males allow “Independent” males to dominate them on the leks.
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