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Incestuous ant escapes inbreeding
By Susan Milius
An odd reproductive biology lets longhorn
crazy ants mate with their siblings without
producing inbred young — and also turns
out to be useful for world domination.
The strange ability may have helped
Paratrechina longicornis become one
of the most widespread invasive ants in
the tropics, says evolutionary biologist
Morgan Pearcy of the Free University of
Brussels. The tiny ants with long antennae, nicknamed crazy ants because they
dash along erratically instead of following foraging trails, now occupy so much
territory that scientists haven’t figured
out where the insect originated.
In lab tests, queens produce some
daughters that are clones of themselves
and that will also become queens. The
queen’s sons — very oddly — turn out
to be genetically identical to her mate.
So a queen’s son can mate with her
daughter in a pairing that’s genetically
equivalent to a pairing of nonsiblings.
The next generation thus does not suffer
the loss of genetic diversity that comes
from brother-sister inbreeding.
There is still some normal sexual gene
shuffling among longhorn crazy ants,
however. When the queen produces
daughters that will grow up to be workers, they turn out to carry the usual blend
of mom’s and dad’s genes, Pearcy and
his colleagues report in a paper posted
online February 2 in the Proceedings of
the Royal Society B.
The novelty of the report is in linking
the biology to the ant’s invasive success,
comments Jürgen Heinze of the University of Regensburg in Germany. Such
double-clone reproduction has been
detected only twice before; the first known
case was in the little fire ant (not the
species bedeviling the southern United
States but an invader all the same).
Pearcy and his colleagues worked
with ants that had been collected in
Bangkok and brought back to the lab
to reproduce in single-queen colonies.
Outdoors, colonies typically have multiple queens, sometimes hundreds, so that
just checking genetic markers in a mul-tiple-queen colony without knowing
which eggs came from which mother
could miss the unusual clonal descent
Ant genome triple play
Nourishing hopes for the fight against
an ant takeover, international research
teams have unveiled genetic blue-
prints for the notori-
ously invasive fire
ant and Argentine
ant. The genome
for a species with a
smaller range, the
red harvester ant (shown here carrying
a seed), appears along with the other
two online January 31 in the Proceed-
ings of the National Academy of Sci-
ences. As well as offering new material
to mine for ideas on pest control, the
studies reveal insights into ant biology.
All three species, for example, show
extraordinary richness in genes for
taste- and smell-detecting molecules:
344 genes for red harvester ants versus 165 for honeybees. — Susan Milius
Nostrils not equal in pigeons
When pigeons sniff their way home,
the right nostril comes in much
handier than the left, researchers
report January 27 in the Journal
of Experimental Biology. Previous
evidence of this asymmetry led an
international team of researchers
Longhorn crazy ants have an unusual
reproductive cycle that lets siblings
mate without genetically inbreeding.
of the reproductive females and males.
Uncovering the system was “a complete accident,” says coauthor Mike
Goodisman of Georgia Tech in Atlanta.
What was supposed to be a routine
genetic analysis as part of another project turned out to have weird results.
Just how that clonal reproduction
works, especially on the male side,
remains to be explored. Pearcy says that
when the news of dual-cloning broke for
the little fire ant in 2005, researchers
suspected that dad’s genes would kick
mom’s genes out of fertilized eggs. Now,
however, he points out another hypothesis: that some trait of the queens lets
them produce “empty eggs” with none of
the queen’s DNA in them at all. So when
sperm reaches the eggs, they become
clones of dad.
From ToP: ALToN N. SPArkS Jr./UNiv. oF GeorGiA; BUGWood.orG/WWW.ALexANder WiLd.com
to investigate 28 homing pigeons
outfitted with GPS devices. The team
plugged either a pigeon’s left or right
nostril and then released the birds
about 40 kilometers from home. While
all the birds headed out in the correct
direction, pigeons with a blocked right
nostril took a more circuitous path,
stopping and exploring more en route,
suggesting that the right nostril is
important for processing navigation-
related odors. The team notes that
people also favor the right nostril when
detecting and evaluating the intensity
of odors, hinting at a broader olfactory
asymmetry. — Rachel Ehrenberg
