Slave-making ant

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Queen and brood of the social parasite Polyergus lucidus with Formica archboldi workers Polyergus lucidus with host Formica archboldi.jpg
Queen and brood of the social parasite Polyergus lucidus with Formica archboldi workers

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.

Contents

The slave-making ants are specialized to parasitize a single species or a group of related species, and they are often close relatives to their hosts, which is typical for social parasites. The slave-makers may either be permanent social parasites (thus depending on enslaved ants throughout their whole lives) or facultative slave-makers. The behavior is unusual among ants but has evolved several times independently.

Terminology

Theft of brood for the purpose of employing the stolen individual's efforts in support of the thief is called dulosis (from Greek δοῦλος , "slave"), but the term "slave-making" is used in older literature and is still common. [1] There is some controversy associated with using the term "slave" and "slave-maker" to describe the natural history of this species. Additionally, there are species commonly raided that are referred to as "negro ant" specifically because they are common victims of ant raids, although this is not endorsed by nomenclature societies [2] and may cause offence. Some have argued that using such non-inclusive metaphors in science is harmful to scientists and interferes with the unbiased scientific process. [3] [4] Suggestions to replace these terms with alternatives include replacing "slave-making ant" with "pirate ant" or "kidnapper ant" and replacing "slave" with "captive". [2]

A related type of social parasitism is called inquilinism, in which a reproductive enters a host colony, lays eggs, and relies on the host colony to rear its offspring. Unlike brood parasitism, the inquiline remains within the nest and typically its brood does not outnumber the host's brood. [1]

Obligate and facultative slave-makers

Slave-making ants may be permanent social parasites, thus depending on enslaved host ants throughout their whole lives and unable to function without them [5] in which case they are termed obligate slave-makers. Alternatively, facultative slave-making ants, like those in the Formica sanguinea complex, represent an intermediate parasitic group, between free-living species and obligatory slave-making species. In laboratory tests, when captured workers were removed from colonies of Formica sanguinea and Polyergus rufescens, the behavior of F. sanguinea changed dramatically within 30 days of their removal, with workers becoming self-sufficient at feeding and brood care. Workers of Polyergus , in contrast, were unable to care for their brood, and experienced high mortality. [6]

Raids

Polyergus lucidus returning from raid on Formica incerta. Two of the latter already incorporated into the mixed colony are visible to the right of the nest entrance. Polyergus lucidus returning from raid on Formica incerta.jpg
Polyergus lucidus returning from raid on Formica incerta . Two of the latter already incorporated into the mixed colony are visible to the right of the nest entrance.

Parasitized nests need to replenish the host workers periodically. This is achieved by raiding other nests in a process called slave raiding. [5] [7] The parasite workers are specialized for conducting raids in a two-step process. First, scouts individually search for potential host nests. When successful, the scout returns to its nest and recruits nest-mates to initiate the raid, during which slave-maker ants seize a brood and bring it back home. [8] A colony may capture 14,000 pupae in a single season. [9] Most slave-raiders capture only the young, but Strongylognathus sp. also enslave adult workers. [10]

In most parasite species, workers mark the way to their nest with pheromones and afterwards fellow slave-makers are attracted within a few seconds. They then go quickly to the targeted host nest, attack it, and carrying as many larvae and pupae as possible, return to their nest following the same trail marked by the pheromone. [7] Rossomyrmex is the only reported slave-maker that exclusively uses adult transport and single recruitment chain instead of pheromones during raids, a behavior probably constrained by the arid habitat; raids take place in early summer when soil surface temperature can reach up to 30 °C (86 °F), a temperature in which pheromones would quickly evaporate. [7]

Workers of the attacked nest can fight or flee. In the host species Proformica , the most common behavior is flee, probably because hosts almost always lose fights. [7] Most studies on the raiding behavior of species in the F. sanguinea complex confirm that slave raiders usually rout their opponents, who typically flee in a state of panicked alarm, and that aggressive encounters, when they occur, are brief and do not result in the death of adult individuals from either species. However, when large colonies of slave species offer resistance during raids prolonged fighting is possible and many workers of both species can be killed. [11]

Later, host workers emerging in the parasite nest will be imprinted on and integrated into the mixed colony where they will rear the parasite brood, feed and groom the parasite workers, defend the nest against aliens (e.g. other insects or spiders), and even participate in raids, [8] including those against their original colony. [12] Altruistic acts of slaves are thus directed toward unrelated individuals. One hypothesis suggests that slave deception is possible because slaves are captured as pupae and learn the slave-maker colony odor after emergence. [13]

However, in some cases, the enslaved ants rebel against their slave-maker ants, killing a large number of the slave-maker ant offspring. [14] This is because "slaves can gain indirect fitness benefits by reducing parasite pressure on nearby host colonies, because these are often closely related to the slaves". [14] Thus, the slave ants protect their native colonies from further raids by slave-maker ants. [14]

Parasite–host pairs

Reproduction

The reproductive behavior of slave-making ants usually consists in synchronous emergence of sexuals followed by a nuptial flight and the invasion of a host nest, [17] but also in some cases females display a mating call around the natal nest to attract males and immediately after mating search for a host nest to usurp. [18]

Only one slave species is usually found in a single Polyergus nest. This is in contrast to related facultative slave-makers of the genus Formica belonging to the F. sanguinea species group, found in the same habitat, whose nests commonly contain two or more species serving as slaves. Choice of a host species can occur both through the colony-founding behavior of queens and through the choice of target nests for slave raids. The parasitic Polyergus queens found colonies either by adoption, where a queen invades the nest of a slave species, killing the resident queen and appropriating workers and brood present, or by "budding", in which a queen invades or is accepted into a host species nest accompanied by workers from her nest of origin. [19]

Evolution

The first hypothesis concerning the origins of slave-making was Darwin's (1859) suggestion in On the Origin of Species that slavery developed as a by-product of brood predation among related species. Other hypotheses focus on territorial interactions with opportunistic brood predation or brood transport among polydomous colonies (consist of multiple nests) as the main pathway to slave-making. [20] [21] Slave-making behavior is unusual among ants but has evolved independently more than ten times in total [10] including in the subfamilies Myrmicinae and Formicinae. [22] [23] Slave-makers and their hosts are often close phylogenetic relatives, [24] which is typical for social parasites and their respective hosts (formalized as Emery's rule). This has major evolutionary implications since it may argue for sympatric speciation. [25]

Raids can jeopardize host colony survival, therefore exerting a strong selection pressure upon the hosts. Reciprocally, there is some evidence that hosts also exert a selection pressure on their parasites in return, since resistance by host colonies might prevent enslavement. Coevolutionary processes between slave-making ant species and their hosts then can escalate to an evolutionary arms race. [8]

See also

Related Research Articles

<i>Tetramorium atratulum</i> Species of ant

Tetramorium atratulum is a rare workerless socially parasitic ant from the Palaearctic region, which has even been introduced together with its host in North America. This extreme inquiline is represented only by female and pupoid type male individuals, whose morphology and anatomy indicate a highly specialized level of parasitism. The body of males is depigmentated, the cuticle is thin, the petiole and postpetiole are widely connected, and degenerate mandibles, palps, and antennae are observed. Female wing venation is reduced and the occipital region is narrowed. Mature females are typically physogastric and found in queenless host nests.

<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 a single ant species able to maintain its 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.

<span class="mw-page-title-main">Harvester ant</span> Common name for several different ants

Harvester ant, is a common name for any of the species or genera of ants that collect seeds, or mushrooms as in the case of Euprenolepis procera, which are stored in the nest in communal chambers called granaries. They are also referred to as agricultural ants. Seed harvesting by some desert ants is an adaptation to the lack of typical ant resources such as prey or honeydew from hemipterans. Harvester ants increase seed dispersal and protection, and provide nutrients that increase seedling survival of the desert plants. In addition, ants provide soil aeration through the creation of galleries and chambers, mix deep and upper layers of soil, and incorporate organic refuse into the soil.

<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>Polyergus breviceps</i> Species of ant

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. 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". 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. 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.

<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>Ectatomma parasiticum</i> Species of ant

Ectatomma parasiticum is a species of ant in the subfamily Ectatomminae. Known from Mexico, the species is a social parasite of the related species Ectatomma tuberculatum. It is the only parasitic species described in the Ectatomminae subfamily, and among the rare inquilines from the tropics.

<i>Lenomyrmex</i> Genus of ants

Lenomyrmex is a Neotropical genus of ant in the subfamily Myrmicinae.

<i>Melophorus bagoti</i> Species of ant endemic to Australia

Melophorus bagoti, the red honey ant, is an Australian species of desert ant in the subfamily Formicinae.

<i>Ectatomma ruidum</i> Species of ant

Ectatomma ruidum is a Neotropical species of ant in the subfamily Ectatomminae.

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

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>Formica pallidefulva</i> Species of ant

Formica pallidefulva is a species of ant found in North America. It is a red to dark brown ant with a shiny body, and varies in shade across its range. Colonies of this ant are found in a variety of habitats, where they excavate underground nests with galleries and chambers. In some parts of its range, the nests may be raided by slave-making ants, most notably Formica pergandei and Polyergus montivagus.

<span class="mw-page-title-main">Symphiles</span>

Symphiles are insects or other organisms which live as welcome guests in the nest of a social insect by which they are fed and guarded. The relationship between the symphile and host may be symbiotic, inquiline or parasitic.

References

  1. 1 2 Breed, Cook & Krasnec 2012, p. 2
  2. 1 2 Herbers, Joan M. (2007-02-01). "Watch Your Language! Racially Loaded Metaphors in Scientific Research". BioScience. 57 (2): 104–105. doi: 10.1641/B570203 . ISSN   1525-3244. S2CID   84617477.
  3. ↑ Taylor, Cynthia; Dewsbury, Bryan M. (2018-03-30). "On the Problem and Promise of Metaphor Use in Science and Science Communication". Journal of Microbiology & Biology Education. 19 (1): 19.1.46. doi:10.1128/jmbe.v19i1.1538. ISSN   1935-7877. PMC   5969428 . PMID   29904542.
  4. ↑ Khan, Aziz (2021-02-08). Deathridge, Julia; Rodgers, Peter (eds.). "A call to eradicate non-inclusive terms from the life sciences". eLife. 10: e65604. doi: 10.7554/eLife.65604 . ISSN   2050-084X. PMC   7870137 . PMID   33556000.
  5. 1 2 Ruano et al. 2013, p. 1
  6. ↑ Topoff & Zimmerli 1991, p. 313
  7. 1 2 3 4 Ruano et al. 2013, p. 3
  8. 1 2 3 Delattre et al. 2012, p. 2
  9. ↑ Topoff 1999, p. 89
  10. 1 2 D'Ettorre & Heinze 2001, p. 68
  11. ↑ Topoff & Zimmerli 1991, pp. 313–314
  12. ↑ Miramontes 1993, p. 6
  13. ↑ Blatrix & Sermage 2005, p. 2
  14. 1 2 3 Pennings et al. 2012
  15. 1 2 3 4 5 6 7 8 9 D'Ettorre & Heinze 2001, p. 69
  16. ↑ Delattre et al. 2012, p. 7
  17. ↑ Mori, D'Ettorre & Le Moli 1994, p. 203
  18. ↑ Ruano et al. 2013, p. 2
  19. ↑ Goodloe & Sanwald 1985, p. 297
  20. ↑ Goodloe & Topoff 1987, p. 298
  21. ↑ Topoff & Zimmerli 1991, p. 309
  22. ↑ King & Trager 2007, p. 70
  23. ↑ Goropashnaya et al. 2012, p. 6
  24. ↑ D'Ettorre & Heinze 2001, p. 70
  25. ↑ Fénéron et al. 2013, p. 1

Sources

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