Polyergus breviceps

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Polyergus breviceps
Polyergus breviceps casent0102822 profile 1.jpg
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Formicinae
Genus: Polyergus
Species:
P. breviceps
Binomial name
Polyergus breviceps
(Emery, 1893)

Polyergus breviceps is a species of ant endemic to the United States. It is a social parasite of other ants, namely of Formica gnava but also of Formica occulta and Formica argentea . [2] Polyergus is an inquiline parasite, having lost its ability to take care of its young and themselves. "The workers do not forage for food, feed the young or the queen, or even clean up their own nest". [3] To survive, Polyergus workers raid Formica nests to steal the pupae—which, once hatched, become workers of the mixed nest. This sort of relationship is not unique, of the approximately 8,800 species of ants, at least 200 have evolved some form of symbiotic relationship with one another. [3] What makes Polyergus special is the way a newly mated queen can, all by herself, take over a Formica nest and start a new colony.

Contents

Slave raids and colony takeovers

Polyergus workers emerge from their nest (a mixed nest where Formica workers are already enslaved) and forage for a suitable raid target. If they find one, the scouts return to the nest, rally the other Polyergus, and head out in a raiding column. If the new target is a Formica nest, the Polyergus incite a "panic-flee" response from the Formica by releasing formic acid and take the Formica pupae back to their nest as slaves. Occasionally, a new queen goes on a raiding column with the other Polyergus. She then, after mating, leaves the column and forages for a suitable Formica nest. [3] Howard Topoff evaluated how the queen takes over a colony. After finding a Formica nest, she finds an entrance and is immediately attacked by Formica workers. The queen responds by biting with her sharp mandibles and releasing a pheromone from her enlarged Dufour's gland that, unlike many other parasitic ants, has a pacifying effect. The queen quickly searches for and locates the Formica queen and, with her adapted mandibles, proceeds to bite and lick various parts of the Formica queen for an average of 25 minutes. [4] "Within seconds of the host queen's death, the nest undergoes a most remarkable transformation". [3] The Formica workers cease to be aggressive to the intruder and start to groom the Polyergus queen as if it were their own. [3] The takeover now complete, the Polyergus queen gains not only a nest, but a worker caste as well. She then lays her eggs and the cycle continues.

Mechanisms

Nearly all slave-making ants, including Polyergus, have mandibular adaptations that help them attack others.

Specific to Polyergus, when the queen first enters a Formica nest she releases a pheromone from her enlarged Dufour’s gland. Topoff did experiments to show that this pheromone has an important facilitative effect in colony usurpation; it reduces the aggression of the defending Formica workers. The researchers took the Dufour’s, pygidial, and poison glands from freshly mated Polyergus queens, using water as a negative control. These were crushed in distilled water to make a solution containing their extracts. Because it was impossible to prevent a Polyergus queen from secreting her own pheromones during a live encounter, they used the harvester ant Pogonomyrmex occidentalis (naturally attacked by Formica) as the subject. These ants were dipped in the above solutions, one ant/solution/test at a time, and placed in a petri dish with three Formica occulta "attackers". They were observed for three minutes to see for how long the Pogonomyrmex was attacked. [5] The results were as follows: "the mean duration of aggression by the Dufour’s gland treatment was 53.3 seconds...The mean duration of aggression for the water, pygidial gland, and poison gland controls were: 143.5 seconds, and 137.2 seconds and 132.2 seconds respectively". [5] Apparently, at some time, Polyergus queens evolved the capacity to passively facilitate colony takeovers.

Topoff and Ellen Zimmerli also did experiments to prove that the Polyergus queen "tricks" the Formica colony by obtaining chemicals from the Formica queen in the process of killing her. In one test, the Formica queen was killed (by flash freezing then thawing) prior to Polyergus contact. Even though it was already dead, the Polyergus queen bit, stabbed, and licked the queen just as if it were alive: and the Polyergus was consequently accepted by the colony. [4] Another test showed that if no Formica queen was present, then Polyergus had little chance of a successful takeover. Clearly, the Formica queen is providing some sort of chemical(s) to the Polyergus queen, however unintentionally. That takeover can occur even if the host queen is dead, but not if she is not present, proves that chemical absorption is important. The Polyergus queen needs only kill one host queen to be accepted. If the colony was polygynistic, the Polyergus queen can take her time finding the other queens. "Hour by hour, day by day, she methodically locates and kills every Formica queen, sometimes taking several weeks to clear out all remnants of opposition". [3]

Evolution

Considerable work has been published on the evolution of ant dulosis and almost all of it has at least some empirical evidence to defend its positions. Notably, that nearly all raiding ant species have is an adaptation of their mandibles that make them big or piercing or both. It makes sense that the very thing that helps an ant be a better raider makes that same ant depend on others. The parasite loses the use of its mandibles for actual work. On this and other evidence, some propose that predation is the precursor to slavery. [6] It has also been suggested that colony multiplication by adoption and budding followed by temporary parasitism can lead to dulosis. While observations indicate that colony multiplication can lead to temporary parasitism, it is apparently very questionable that temporary parasitism leads to dulosis. [6]

In addition, about 100 years ago, Carlo Emery observed that, "The slave-making temporarily and permanently parasitic ants originate from closely related forms which serve them as host." [7] Jurgen Heinze did a series of experiments that prove this observation, known today as Emery's Rule. Rather than just relying solely on morphological cues, he used enzyme gel electrophoresis assays to create a detailed phylogenetic picture of host and parasite connections. [8] His experimental results support a loose version of Emery’s rule. On one end of the spectrum, they saw near identical electromorphs between species in most host and parasite pairs studied. However, it also appears that at least one example does not support Emery’s rule in that ( Leptothorax paraxenus ) differed from its host in several electromorphs. [8] The selective forces involved in the evolution of social parasitism are not fully understood, and it is unlikely that one model fits all relationships.

"Any hypothesis explaining the evolution of slavery in Polyergus must account both for the origin of group raiding with brood capture, and for non-independent colony foundation by queens". [9] Topoff gives an adequate hypothesis to the evolution of Polyergus by integrating three processes: queen takeover, olfactory imprinting, and territorial fighting. [9] Here are his main points. A free-living ancestor of Polyergus, that is a scavenger, would band together with others for intraspecific contest. Occasionally a queen invaded colonies of Formica. Initially the queen drove off the Formica queen and workers and appropriated the Formica pupae (he gives as example the queens of Formica wheeleri that do this now). The killing of the Formica queen and adoption by the workers evolved from this. His previous work (which was presented earlier) shows what would have evolved for adaptation to occur: "(1) sharp mandibles for killing the Formica queen, (2) a pheromone that reduces aggression from resident workers, (3) a tendency to hold onto the dead Formica queen long enough to absorb her odors...". [3] The next step was olfactory imprinting between the two species, a consequence of living one’s life from start to finish in the presence of both species. Polyergus’ ancestor then forages and encounters a colony of the same species. Again, they recruit nestmates to a territorial raid. In a brilliant insight, Topoff suggest this trait explains the raiding behavior. The Polyergus worker, raised by Formica as conspecifics, "identifies individual of Formica as belonging to its own species, another territorial raid is incited. Thus from the standpoint of Polyergus... slave raids are equivalent to territorial raids". [9] The captured brood is imprinted as well and they become workers in the original nest. As time went on "Our ancestral Polyergus could easily slide in the direction of facultative parasitism". [9] Eventually, Polyergus ancestors lost the ability to take care of themselves and become the inquiline Polyergus we see today.

Related Research Articles

<span class="mw-page-title-main">Ant</span> Family of insects

Ants are eusocial insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from vespoid wasp ancestors in the Cretaceous period. More than 13,800 of an estimated total of 22,000 species have been classified. They are easily identified by their geniculate (elbowed) antennae and the distinctive node-like structure that forms their slender waists.

<i>Formica</i> Genus of ants

Formica is a genus of ants of the family Formicidae, including species commonly known as wood ants, mound ants, thatching ants, and field ants. Formica is the type genus of the Formicidae, and of the subfamily Formicinae. The type species of genus Formica is the European red wood ant Formica rufa. Ants of this genus tend to be between 4 and 8 mm long. Ants belonging to the Formica genus possess a single knob or bump located between their thorax and abdomen. These ants primarily feed on honeydew, a sugary liquid produced by aphids. Formica ants appear to take on a shepherding role with smaller aphids, relocating them to different parts of plants to ensure a continuous food source for the aphids. By doing so, the ants can establish a relatively sustainable honeydew supply for both themselves and their colony.

<i>Formica cunicularia</i> Species of ant

Formica cunicularia is a species of ant found all over Europe. They are especially common in western Europe and southern England, but they can be found from southern Scandinavia to northern Africa and from Portugal to the Urals. In England, Donisthorpe records the species as having occurred as far north as Bewdley in Worcestershire. In Formica cunicularia, the worker is an ashy grey black color and is usually 4.0–6.5 mm long. The males are found to have a uniformly dark body and are 8.0–9.0 mm long. The queen is yellowish red to dark black and is 7.5–9.0 mm.

<span class="mw-page-title-main">Ant colony</span> Underground lair where ants live, eat, and tend eggs

An ant colony is a population of ants, typically from a single species, capable of maintaining their complete lifecycle. Ant colonies are eusocial, communal, and efficiently organized and are very much like those found in other social Hymenoptera, though the various groups of these developed sociality independently through convergent evolution. The typical colony consists of one or more egg-laying queens, numerous sterile females and, seasonally, many winged sexual males and females. In order to establish new colonies, ants undertake flights that occur at species-characteristic times of the day. Swarms of the winged sexuals depart the nest in search of other nests. The males die shortly thereafter, along with most of the females. A small percentage of the females survive to initiate new nests.

<i>Polyergus</i> Genus of ants

Polyergus is a small genus of ants with 14 described species. They are also referred to by the names "slave-raiding ants" and "Amazon ants". They are characterized by their habit of raiding nests for workers.

<i>Harpagoxenus sublaevis</i> Species of ant

Harpagoxenus sublaevis is a species of ant in the subfamily Myrmicinae. It is found in Austria, France, Germany, Italy, and Switzerland.

Myrmecia inquilina is a species of ant endemic to Australia in the subfamily Myrmeciinae, first discovered in 1955 and described by Athol Douglas and William Brown Jr. in 1959. These ants are large, measuring 21.4 millimetres (0.84 in). During the time of its discovery, Douglas and Brown announced M. inquilina as the first social parasite among the primitive subfamilies, and today it is one of the two known Myrmecia species to have no worker caste. Two host species are known, Myrmecia nigriceps and Myrmecia vindex. Aggression between M. inquilina and its host species does not occur, and colonies may only produce M. inquilina brood months after the inquiline queens begin to lay their eggs. Queens eat the colony brood or trophic eggs, and other Myrmecia species may kill M. inquilina queens if they reject them. Due to its restricted distribution and threats to its habitat, the ant is "vulnerable" according to the IUCN Red List.

<i>Polyergus lucidus</i> Species of ant

Polyergus lucidus is a species of slave-making ant in the subfamily Formicinae endemic to the eastern United States. It is an obligatory social parasite, unable to feed itself or look after its brood and reliant on ants of another species of the genus Formica to undertake these tasks. Parasitic ants are known as "dulotics" and the ants they parasitise are known as "hosts".

<i>Polyergus samurai</i> Species of ant

Polyergus samurai is a species of slave-making ant in the subfamily Formicinae.

<i>Rossomyrmex</i> Genus of ants

Rossomyrmex is a genus of slave-making ant in the subfamily Formicinae. The genus consists of four species, each with a single host from the genus Proformica, and has a very wide range of distribution from China to southeastern Spain, from huge extended plains to the top of high mountains.

<i>Formica sanguinea</i> Species of ant

Formica sanguinea, or blood-red ant, is a species of facultative slave-maker ant in the genus Formica characterized by the ability to secrete formic acid. It ranges from Central and Northern Europe through Russia to Japan, China, the Korean Peninsula, Africa and also the United States. This species is coloured red and black with workers up to 7 mm long.

<i>Bombus bohemicus</i> Species of bee

Bombus bohemicus, also known as the gypsy's cuckoo bumblebee, is a species of socially parasitic cuckoo bumblebee found in most of Europe with the exception of the southern Iberian Peninsula and Iceland. B. bohemicus practices inquilinism, or brood parasitism, of other bumblebee species. B. bohemicus is a generalist parasite, successfully invading several species from genus Bombus. The invading queen mimics the host nest's chemical signals, allowing her to assume a reproductively dominant role as well as manipulation of host worker fertility and behavior.

<i>Polyrhachis</i> Genus of ants

Polyrhachis is a genus of formicine ants found in the Old World with over 600 species. The genus is yet to be comprehensively resolved and contains many varied species including nest-weavers, swimming workers, soil and tree-dwellers. First fossil record of this genus was P. annosa from Miocene.

<i>Dolichovespula adulterina</i> Species of wasp

Dolichovespula adulterina is a species of parasitic social wasp found in the Palearctic region. D. adulterina feeds on a variety of foods, including insects, spiders, arthropods, meat, molluscs, fruit, nectar, and larval secretions. D. adulterina was formerly considered to be synonymous with D. arctica from the Holarctic region, but more recent research indicates that D. arctica is a separate species.

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Vespula squamosa, or the southern yellowjacket, is a social wasp. This species can be identified by its distinctive black and yellow patterning and orange queen. This species is typically found in eastern North America, and its territory extends as far south as Central America. Within these territories, they create enormous, multiple-comb nests. The colonies may be either annual or perennial depending on the climate, and in many perennial nests, polygyny takes place. In addition, this species uses pheromones both as a sexual attractant and an alarm signal. This species feeds on insects and animal carcasses; it does not produce honey. V. squamosa, a social insect, has developed a parasitic relationship with the species V. vidua and V. maculifrons. Due to their painful, venomous stings, the species is considered a pest.

<span class="mw-page-title-main">Slave-making ant</span> Species of ants that steal young ants of another species to contribute to their colony

Slave-making ants or slaver ants are brood parasites that capture broods of other ant species to increase the worker force of their colony. After emerging in the slave-maker nest, slave workers work as if they were in their own colony, while parasite workers only concentrate on replenishing the labor force from neighboring host nests, a process called slave raiding.

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Polyergus rufescens is a species of slave-making ant native to southern Europe and parts of Asia, commonly referred to as the European Amazon ant or as the slave-making ant. It is an obligatory social parasite, unable to feed itself or look after the colony and reliant on ants of another species to undertake these tasks. To replenish these servant ants, it raids nearby ant colonies and carries home pupae and larvae, and these are reared to provide future workers for the colony. A newly mated female P. rufescens needs to make its way into one of these "host" nests, kill the host queen, and be accepted by the host workers in her place.

<i>Polyergus mexicanus</i> Species of ant

Polyergus mexicanus is a species of slave-making ant in the subfamily Formicinae. It is the most widely distributed species of Polyergus in North America. It is an obligatory social parasite, unable to feed itself or look after the colony and reliant on ants of another species, Formica, to undertake these tasks. The parasitic ants are known as "dulotics" and the ants they parasitise are known as "hosts".

<i>Formica incerta</i> Species of ant

Formica incerta is a species of ant found in eastern North America. It is the most common species of Formica in many areas, and excavates underground nests with small entrance holes. Its diet includes nectar produced by extrafloral nectaries and honeydew, which it obtains from aphids and treehoppers. It is the main host for the slave-making ant Polyergus lucidus. F. incerta was first described by Italian entomologist Carlo Emery in 1893. Its specific name comes from the Latin incertus meaning "uncertain" and seems particularly apt given the subsequent uncertainty as to the validity of the species and the difficulty in distinguishing this ant from other species living in the same area.

<i>Vespula infernalis</i> Species of wasp

Vespula infernalis is an obligate parasitic wasp, parasitizing the nests of other species in the genus Vespula. Its common host species is V. acadica in North America. It is sometimes called the cuckoo yellowjacket wasp due to its inquiline lifestyle. They differ from other parasitic wasps in their intensely aggressive behaviour during invasion and occupation of the host colony. Several morphological adaptations such as bigger body parts and highly curved stingers are present in these wasps to aid their aggressive parasitic behaviour.

References

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  7. Carlo Emery (1909). "Ueber den Ursprung der dulotischen, parasitischen und myrmekophilen Ameisen". Biologisches Centralblatt. 29: 352–362.
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