Intraspecific differences in male ruffe wading birds (Calidris pugnax) are due to a supergene, a group of genes
Ruff is one of the representatives of waders.These birds live in swamps and wet meadows in the north of Eurasia. A feature of this species is a pronounced intraspecific diversity among males. Scientists distinguish three types of male ruffs, which differ in their shape and behavior: independent males, satellites and faders.
Independent males are large individuals thatshow pronounced aggression and compete for the attention of females. This is the most numerous variation. Satellites are slightly smaller in size, they try to unite with independent males. The most interesting and rare type are faders. These males mimic females in appearance and behavior in order to bypass aggressive competitors, join the female team and easily achieve mating. This leads the faders to a significant reproductive success.
Three types of male ruff: independent (back), satellites (right) and fader (foreground). Photo: Clemens Küpper/Max Planck Institute for Ornithology
The difference between the types of males is due to their DNA.About 3.8 million years ago, an inversion occurred as a result of a mutation. Faders are carriers of this gene variation. Satellites are a later form, resulting from the recombination of genes between the original and mutated variants.
Such gene variations are found not only inmales, but also in females, however, do not lead to significant differences in size and behavior. Studies of the effect of the supergene on females have not previously been conducted. In their work, the scientists showed that, despite the absence of external differences, female faders lay almost half as many eggs as independent ones. At the same time, due to low fitness, the number of chicks that survive to adulthood in female faders is already eight times less.
Extremely high competition among independent males has led to the creation of larger and more aggressive individuals.But they concentrate their attention and compete only with their own kind.This opens up a niche for faders, masters of deception.
“Our research shows that there is no suchconcepts as a more adapted individual,” notes Clemens Küpper. — Diversity wins even under strong selection pressure. The emergence of new forms is the main principle of life.”
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