One bird's joy is another bird's sorrow

Date:
March 17, 2022
Source:
Max-Planck-Gesellschaft
Summary:
A genetic conflict between the sexes promotes intraspecific
diversity in ruffs. Ruffs are characterized by three supergene
variants that lead to different appearances and courtship behavior
in males. Whether these variants affect females was previously
unknown. Researchers now show that females of the so-called Faeder
variant produce less offspring. However, this female handicap helps
their males: Disguised as females, Faeder males benefit from their
own rarity and obtain more matings. The contrasting effect of the
variant in males and females thus contributes to its persistence
over time. The study thereby provides important insights into the
mechanisms that maintain biodiversity.



FULL STORY ==========================================================================
A genetic conflict between the sexes promotes intraspecific diversity
in ruffs.

Ruffs are characterized by three supergene variants that lead to different appearances and courtship behavior in males. Whether these variants affect females was previously unknown. Researchers at the Max Planck Institute
for Biological Intelligence, in foundation (i.f.), now show that females
of the so- called Faeder variant produce less offspring. However, this
female handicap helps their males: Disguised as females, Faeder males
benefit from their own rarity and obtain more matings. The contrasting
effect of the variant in males and females thus contributes to its
persistence over time. The study thereby provides important insights
into the mechanisms that maintain biodiversity.


==========================================================================
The question of how biodiversity arises and is maintained is not only
of central importance to biologists. Biodiversity is most prominently associated with species diversity, but one can also find a substantial
amount of diversity within many species. For example, there are various
and pronounced differences between males and females.

Ruffs (Calidris pugnax) are a particularly vivid example of intraspecific diversity that goes beyond typically observed sex differences. In
these sandpipers, males will take up one of three morphs that differ
in appearance and behavior. Most males are Independents with rather
dark plumage ornaments that aggressively defend a small display
territory in mating arenas to impress visiting females. The somewhat smallerSatellites, recognizable by their lighter plumage, display more
solemnly in an alliance with an Independent host. The rare Faeder males
have an entirely different tactic: they resemble females and sneak around
the mating arenas unnoticed by the other males.

Remarkably, which tactic a male ruff will use, is written in his
genes. About four million years ago, a 'supergene' emerged through a
genomic accident: a DNA fragment broke out of a chromosome and reinserted itself in the opposite direction. This inversion was the birth of the
Faeder morph. The affected DNA region contains about 100 genes and is
inherited as a functional unit. A rare recombination between the original
and the inverted DNA sequence subsequently gave rise to the Satellites.

Interestingly, the supergene is not located on a sex chromosome,
so the different genetic variants also occur in females. Unlike in
males, however, little was known whether and how they affect females. An international team led by Clemens Ku"pper at the Max Planck Institute for Biological Intelligence, i.f., and David Lank at Simon Fraser University,
now compared the reproductive success of the female morphs. They found
that female Faeders have significantly lower reproductive success as
they lay fewer and smaller eggs. In addition, their embryos as well,
as ruff chicks hatching from smaller eggs, have lower survival rates.

Nevertheless, the Faeder variant has not gone extinct. To understand
how it can persist, the researchers modeled different scenarios. The
models showed that an increased reproductive success of Faeder males is necessary to maintain the Faeder variant.

"The Faeder supergene brings a big disadvantage for females, but it is
an advantage for males," explains Lina Giraldo-Deck, lead author of the
study. "We think that exactly this genetic conflict between males and
females contributes to the maintenance of the Faeder variant." Indeed,
the females' low reproductive success plays into the males' hands: the
less common Faeder males are, the better their stealthy strategy works.

However, Faeders rely on the Independent ruffs. Faeder and Satellite
gene variants are not viable on their own. Hence, each ruff carries
at least one Independent supergene variant. In addition, male Faeders
exploit the courtship efforts of the Independents, and Faeder chicks
are raised primarily by female Independents.

"Today's male Independents seem rather defenseless against the Faeders' tactics," says Clemens Ku"pper. "The extremely high competition among Independents led to the evolution of larger and more aggressive males.

Meanwhile, they have become operation-blind and focus in their competition primarily on similar-looking males. This opens up a niche for deception
artists like the Faeders, who exploit it very effectively." This shows
that there is no such thing as 'the fittest' who can cope with all
challenges. "Diversity prevails even under strong selective pressure. The emergence of new forms is a principle of all life," notes Clemens Ku"pper.

Next, the scientists plan to investigate the effect of the supergene
variants on other life stages and how the genes involved influence the physiology of the growing animals -- this, the researchers emphasize,
is the only way to understand the underlying evolutionary mechanisms in
their entirety.


========================================================================== Story Source: Materials provided by Max-Planck-Gesellschaft. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Lina M. Giraldo-Deck, Jasmine L. Loveland, Wolfgang Goymann, Barbara
Tschirren, Terry Burke, Bart Kempenaers, David B. Lank, Clemens
Ku"pper.

Intralocus conflicts associated with a supergene. Nature
Communications, 2022; 13 (1) DOI: 10.1038/s41467-022-29033-w ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/03/220317094711.htm

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