As expected, Temnothorax
are under strong selective pressure to evolve parasite-resistant
adaptations, just as Myrmonexus are
under pressure to overcome such resistance. These mutually competitive
host-parasite relationships, which sometimes escalate to so-called “evolutionary arms races”, are an
important aspect of coevolution.
In order to effectively resist parasitic intruders in their
colonies, Temnothorax hosts need a
way to distinguish between “friends” and “foes”. They do so by analyzing the
cuticular hydrocarbon profile, which is the array of chemicals found on the
surface of the ant’s body. Intruder Myrmonexus
have within their hydrocarbon profile various compounds that are unpleasant
to host Temnothorax, who in turn use
this chemical signature to identify the parasites. Once they have identified an
intruder, Temnothorax aggressively
bite and eject it from the colony. In response to this adaptation from the
host, parasitic Myrmonexus constantly
alter the chemical signature of their bodies by, among other things, adapting
the hydrocarbon profile of Temnothorax they
had previously captured.
A team of scientists led by Dr Olivier Delattre tried to
identify how effectively the Temnothorax are
able to guard their nests against parasites. Several dozen ant colonies were
observed, including Temnothorax sub-species
that did and did not experience frequent parasitic attacks from the
slave-making Myrmonexus. The
scientists hypothesized that Temnothorax,
if they are to keep up with Myrmonexus
in the coevolutionary arms race, must act much more aggressively towards
parasitic intruders than ants of
other Temnothorax subspecies.
According to the team’s results, Temnothorax do, in fact, react more aggressively towards Myrmonexus in their nests, and they make
the distinction based on the cuticular hydrocarbon profiles of the intruders.
However, a significant portion of ants that were aggressively bitten and
ejected by Temnothorax were actually
fellow Temnothorax sub-species from a
different colony.
The following explanation could be offered for the large
number of non-parasitic ants attacked by Temnothorax:
it is possible that at this point in time Myrmonexus are, in fact, ahead in the arms race, having adapted
their hosts’ chemical signature to such a degree that even Temnothorax have trouble distinguishing their kin from the
slave-makers. The team proposes follow-up studies that would track both the
social behavior and hydrocarbon profiles of Temnothorax
and Myrmonexus to find out
whether the hosts will be able to perfect their ability to discriminate against parasites
while keeping their own kind safe.
Word count: 444
Source cited:
Delattre, Olivier, et al. "Do host species evolve a
specific response to slave-making ants?" Frontiers in Zoology. 9.38 (2012).
Image Source: National Geographic
this is interesting. I have read a bit about how the slaves will act to sabotage their masters and have been known to kill infants in the nurseries. I wonder where their violent tendencies toward the young come from?
ReplyDeleteIt's interesting to see how closely species will interact and influence the other's evolution! If the scientists' hypothesis that the ants are currently experiencing evolution, it will be really interesting to see the consequences of the host species' evolution on the survival of the slave species and the two species' symbiosis.
ReplyDeleteIt is very fascinating how these two species of ant are constantly having to evolve to better assure their survival in their shared environment. Perhaps another reason why the Temnothorax even attack fellow Temnothorax sub-species has to with better ensuring the safety of their own particular colony. Since altruism in the wild is usually only limited to family members, it is not overly surprising that the Temnothorax would attack those they consider to be outsiders. This would especially hold true for those sub-species that are not frequently attacked by the Myrmonexus, as their defense mechanisms might not be as advanced. This in turn could lead to a potential weakness in the colony, making the Temnothorax more susceptible to Myrmonexus attack.
ReplyDelete