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Gamergate (ant)

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For other uses, seeGamergate.

Lateral view of anOphthalmopone berthoudiworker, the ant for which the termgamergatewas originally coined[note 1]

Agamergate(/ˈɡæmərˌɡeɪt/GAMM-ər-gayt) is a matedworker antthat can reproduce sexually, i.e., lay fertilized eggs that will develop as females. In the vast majority of ant species, workers are sterile and gamergates are restricted to taxa where the workers have a functional sperm reservoir ('spermatheca'). In some species, gamergates reproduce in addition to winged queens (usually upon the death of the original foundress), while in other species the queen caste has been completely replaced by gamergates. In gamergate species, all workers in a colony have similar reproductive potentials, but as a result of physical interactions, a dominance hierarchy is formed and only one or a few top-ranking workers can mate (usually with foreign males) and produce eggs. Subsequently, however, aggression is no longer needed as gamergates secrete chemical signals that inform the other workers of their reproductive status in the colony.

Depending on the species, there can be one gamergate per colony (monogyny) or several gamergates (polygyny). Most gamergate species have colonies with a few hundred or fewer workers.

Etymology[edit]

Gamergatederives from the Greek wordsγάμος(gámos) andἐργάτης(ergátēs) and means 'married worker'. It was coined in 1983 by geneticistWilliam Louis Brown[1]and was first used in scientific literature by entomologistsChristian PeetersandRobin Crewein a 1984 paper published inNaturwissenschaften.[2]The definition typically found in entomological dictionaries is 'mated, egg-laying worker',[3][4]and is drawn from the glossary ofBert HölldoblerandE. O. Wilson's 1990 book,The Ants.[3]

Description[edit]

There are 100–200 different species in which gamergates reproduce (roughly 1% of all ants), most of which fall within theponeromorph subfamilies.Whereas workers (which are all females) in most ant species aremorphologicallyincapable of storing sperm, in gamergate species one or several workers mate and have activeovaries.[5]Gamergate lifespan is short compared to queens inqueenrightcolonies, but gamergates can be replaced by other dominant workers in the colony without risking colony survival. Reproductive investment in gamergate females is thus optimized because non-differentiated gamergates (i.e. reproductively inactive workers) function as laborers.[6]

Caste structure[edit]

Dorsal view of a nonreproductive femaleDiacamma australeworker, lacking anterior thoracic gemmae (buds).

Within gamergate colonies, all workers are born reproductively viable and are thus potential gamergates. Prior to differentiation as a gamergate, a dominant worker must physically inhibit its sisters. For example, in the case ofDiacamma australe,the first female to become reproductively active will clip off thethoracicgemmae of her sisters, thus greatly reducing their sexual attractiveness. In other genera, persistent domination of worker females by gamergates via physical aggression all but ensure that they will not produce male offspring.[7]InDiacamma nilgiri,gamergates use dominance interactions to monopolize reproduction without mutilation of sister workers.[8]The same is true forStreblognathus peetersi,which engage in non-injurious aggression to determine dominance.[2]For most gamergate species, the start of ovarian activity eliminates the need to physically dominate nestmate workers. Instead newly producedpheromonesor signaling chemicals ensure that workers remain nonreproductive. Although it is unknown to what degree these chemicals act as pheromones or as signals, support for the signaling hypothesis can be found in the loss of reproductive inhibition of workers as the gamergate grows older and herfecunditydiminishes.[7]

Mechanisms of gamergate replacement vary among monogynous and polygynous species. When a gamergate dies, it is usually replaced by a formerly submissive worker who proceeds to mate and begins ovarian activity. A new gamergate often originates from a youngercohort.For example, when the original founding queen dies in aHarpegnathos saltatorcolony, younger workers begin to fight for dominance and some become the next reproductives.[9]Because reproductively inactive workers are able to activate their ovaries after the death of the gamergate, some gamergate species can be consideredcooperative breedersrather than trulyeusocial insects.[10]

In colonies with both queens and gamergates, the latter function as secondary reproductives.[5]Research onAmblyoponinaespecies has shown that there is a fecundity-based hierarchy among gamergates. InStigmatomma reclinatum,it was found that higher-ranked gamergates had more fully developedoocytesthan low-ranked gamergates.[11]InStreblognathus peetersi,only the alpha worker mates and becomes the gamergate; younger workers await a chance to reproduce when the current gamergate exhibits decreased fecundity or dies.[2]Challenges to gamergates from subordinate workers are risky because the gamergate in species likeDinoponera quadricepsmay mark the challenger by rubbing special chemicals produced only by the gamergate. These chemicals signal to other workers to immobilize the challenger by biting her appendages and immobilizing her for a few days until herhormonallevels return to normal.[12]Subordinate workers play an important policing role in theselection offuture gamergates and are thus able to increase their indirect fitness.[5]

Social structure variation and ecology[edit]

There is much variation in the social structure of ant colonies with gamergates. Some species such asHarpegnathos saltator,[13]Pseudoneoponera tridentata,Gnamptogenys menadensis,andRhytidoponera confusahave a wingedalatequeen caste as well as gamergates.[14]Queenless species with only gamergates and workers may have amonogynousstructure with a single gamergate or they may have apolygynousstructure with multiple gamergates. Examples of monogynous queenless species includePachycondyla krugeri,P. sublaevis,Diacamma australe,D. rugosum,Dinoponera quadriceps,Platythyrea lamellosa,andStreblognathus aethiopicus.[15]Examples of polygynous queenless species includeOphthalmopone berthoudi,O. hottentota,[16]and all known queenless species ofRhytidoponera.[15]In the queenlessOphthalmopone berthoudi,foreign males visit underground nests to mate with young workers.[17]

Ecologically, gamergate species from differenttribesandgeneraoften tend to share certain characteristics. Many gamergate species are solitary generalist foragers living inaridenvironments.[6]Similar to species withergatoidqueens, the evolution of gamergate reproduction is hypothesized to be associated with a shift tocolonial fission.Myrmecologists Christian Peeters andFuminori Itohave also suggested that "the evolution of gamergate reproduction appears strongly associated with the adaptive benefits of secondary polygyny (e.g. increased colony lifespan and resource inheritance), and it is the preferred option in species having workers able to store sperm."[14]

Classification dispute[edit]

The utility ofgamergateas a morphological designation is not without critics. Within the field ofmyrmecologyit is a matter of dispute whethercasteshould be defined primarily by reproductive role or by physical morphology. Notably,Alfred Buschingerhas argued that the termworkershould be applied only to those ants who make up the non-reproductive caste andqueenshould be applied only to reproductively viable female ants regardless of their physical appearance. Hölldobler and Wilson suggest that the two positions can be semantically resolved and that the most fruitful approach would be to keep classification "somewhat loose, incorporating either anatomy or roles in a manner that maximizes convenience, precision, and clarity of expression."[18]

Genera with gamergates[edit]

This list may be incomplete and may require expansion:

See also[edit]

Notes[edit]

  1. ^In the originalNaturwissenschaftenpaper where the term "gamergate" was first used,O. berthoudiis referred to by the synonymPachycondyla berthoudi.
  2. ^Throughout Ito's 1993 paper for theJournal of Natural History,he refers not toStigmatommabut toAmblyopone.At the timeStigmatommawas considered to be a synonym ofAmblyopone.

References[edit]

  1. ^Peeters, Christian; Crewe, Robin (1984). "Insemination Controls the Reproductive Division of Labour in a Ponerine Ant".Naturwissenschaften.71(1): 50–51.Bibcode:1984NW.....71...50P.doi:10.1007/BF00365989.ISSN0028-1042.S2CID43871631.
  2. ^abcVéron, Géraldine (February 2005)."La reine des fourmis couronnée au combat".Le Journal du CNRS(181): 50–51.ISSN0994-7647.Archived fromthe originalon 10 February 2005.Retrieved9 September2014.
  3. ^abBarrows, Edward M. (2011). "Caste – Gamergate".Animal Behavior Desk Reference: A Dictionary of Animal Behavior, Ecology, and Evolution(Third ed.). CRC Press. p. 75.ISBN9781439836514.
  4. ^Gordh, Gordon(2011). "Gamergate".A Dictionary of Entomology.CABI.p. 608.ISBN9781845935429.
  5. ^abcNoël, Carine (6 September 2002)."How queenless ants regulate their conflicts"(Press release). Paris:CNRS.Archived fromthe originalon 2 March 2003.Retrieved10 September2014.
  6. ^abChoe, Jae C.;Crespi, Bernard J.(1997). "Morphologically 'Primitive' Ants".The Evolution of Social Behaviour in Insects and Arachnids.Cambridge University Press.p.385.ISBN9780521589772.
  7. ^abBourke, Andrew F. G. (1995). "7 – Kin Conflict: Reproduction (Part 2 – Queen Policing, Queen Control, and Queen Signaling)".Social Evolution in Ants: Monographs in behavior and ecology.Princeton University Press.pp. 239–240.ISBN9780691044262.
  8. ^Cournault, Laurent; Peeters, Christian (2012). "Aggression regulates monogyny in non-mutilatingDiacammaants ".Insectes Sociaux.59(4): 533–539.doi:10.1007/s00040-012-0251-9.S2CID16179257.
  9. ^Gorman, James (27 May 2014)."The Ant Queen Is Dead. Let the Battles Begin".The New York Times.ISSN0362-4331.Retrieved12 August2014.
  10. ^Crespi, Bernard J. (1996). "9 – Comparative Analysis of the Origins and Losses of Eusociality: Causal Mosaics and Historical Uniqueness (Part 6 – Formicidae)". In Martins, Emília P. (ed.).Phylogenies and the Comparative Method in Animal Behavior.Oxford University Press.p. 272.ISBN9780195092103.
  11. ^abIto, Fuminori (1993). "Social organization in a primitive ponerine ant: queenless reproduction, dominance hierarchy and functional polygyny in Amblyopone sp. (reclinata group) (Hymenoptera: Formicidae: Ponerinae)".Journal of Natural History.27(6): 1315–1324.doi:10.1080/00222939300770751.ISSN0022-2933.
  12. ^Monnin, Thibaud; Ratnieks, Francis L. W.; Jones, Graeme R.; Beard, Richard (5 September 2002)."Pretender punishment induced by chemical signalling in a queenless ant"(PDF).Nature.419(6902): 61–65.Bibcode:2002Natur.419...61M.doi:10.1038/nature00932.ISSN0028-0836.PMID12214231.S2CID4372841.
  13. ^Peeters, Christian;Hölldobler, Bert(November 1995)."Reproductive cooperation between queens and their mated workers: The complex life history of an ant with a valuable nest".Proceedings of the National Academy of Sciences of the United States of America.92(24): 10977–10979.Bibcode:1995PNAS...9210977P.doi:10.1073/pnas.92.24.10977.ISSN0027-8424.PMC40553.PMID11607589.
  14. ^abPeeters, Christian; Ito, Fuminori (2001). "Colony Dispersal and the Evolution of Queen Morphology in Social Hymenoptera".Annual Review of Entomology.46:601–30.CiteSeerX10.1.1.562.7031.doi:10.1146/annurev.ento.46.1.601.ISSN0066-4170.PMID11112181.
  15. ^abPeeters, Christian P. (1991). Veeresh, G. K.; Mallik, B. (eds.).Social Insects and the Environment: Proceedings of the 11th International Congress of IUSSI, 1990 (International Union for the Study of Social Insects).Brill Academic Pub. p. 234.ISBN978-9004093164.Retrieved12 August2014.
  16. ^Peetere, C. P.; Crewe, R. M. (1985)."Queenlessness and reproductive differentiation inOphthalmopone hottentota".South African Journal of Zoology.20(4): 268.doi:10.1080/02541858.1985.11447948.
  17. ^"Species:Pachycondyla berthoudi".antweb.org.AntWeb.Retrieved12 August2014.
  18. ^Hölldobler, Bert;Wilson, E. O.(1990). "Caste and Division of Labor".The Ants.Harvard University Press.pp.301 & 305.ISBN9780674040755.
  19. ^Gobin, B.; Peeters, C.; Billen, J. (September 1998)."Production of trophic eggs by virgin workers in the ponerine ant Gnamptogenys menadensis"(PDF).Physiological Entomology.23(4): 329–336.doi:10.1046/j.1365-3032.1998.234102.x.S2CID83569093.Archived fromthe original(PDF)on 27 August 2016.Retrieved26 August2016.
  20. ^Peeters, Christian P. (1987). "The Reproductive Division of Labour in the Queenless Ponerine Ant Rhytidoponera sp. 12".Insectes Sociaux.34(2): 75–86.doi:10.1007/BF02223826.ISSN0020-1812.S2CID26116621.
  21. ^abcdefghijkSchmidt, C. A; Shattuck, S. O. (2014). "The Higher Classification of the Ant Subfamily Ponerinae (Hymenoptera: Formicidae), with a Review of Ponerine Ecology and Behavior".Zootaxa.3817(1): 1–242.doi:10.11646/zootaxa.3817.1.1.PMID24943802.S2CID4540972.
  22. ^"Genus:Diacamma".antweb.org.AntWeb.Retrieved12 August2014.
  23. ^Haskins, Caryl Parker;Zahl, P. A. (1971)."The reproductive pattern of Dinoponera grandis Roger (Hymenoptera, Ponerinae) with notes on the ethology of the species".Psyche.78(1–2): 1–11.doi:10.1155/1971/914147.ISSN0033-2615.
  24. ^Peeters, C.; Fisher, B.L. (14 March 2016)."Gamergates (mated egg-laying workers) and queens both reproduce in Euponera sikorae ants from Madagascar"(PDF).African Entomology.24(1): 180–187.doi:10.4001/003.024.0180.S2CID51851380.Retrieved26 August2016.
  25. ^Peeters, Christian;Hölldobler, Bert(2000). "Sexual reproduction by both queens and workers in the ponerine antHarpegnathos saltator".Insectes Sociaux.47(4): 325–332.doi:10.1007/PL00001724.ISSN0020-1812.S2CID8728206.
  26. ^Peeters, Christian; Crewe, Robin M. (1985)."Worker reproduction in the ponerine ant Ophthalmopone berthoudi: an alternative form of eusocial organization".Behavioral Ecology and Sociobiology.18(1): 29–37.doi:10.1007/BF00299235.ISSN0340-5443.S2CID20041163.
  27. ^Schilder, Klaus; Heinze, Jürgen;Hölldobler, Bert(January 1999). "Colony structure and reproduction in the thelytokous parthenogenetic antPlatythyrea punctata(F. Smith) (Hymenoptera, Formicidae) ".Insectes Sociaux.46(2): 150–158.doi:10.1007/s000400050126.ISSN0020-1812.S2CID13729041.
  28. ^"Genus:Streblognathus".antweb.org.AntWeb.Retrieved12 August2014.
  29. ^Dietemann, V.; Peeters, C;Hölldobler, B.(2004). "Gamergates in the Australian ant subfamily Myrmeciinae".Naturwissenschaften.91(9): 432–435.Bibcode:2004NW.....91..432D.doi:10.1007/s00114-004-0549-1.ISSN0028-1042.PMID15278223.S2CID26161972.
  30. ^Hölldobler, Bert; Liebig, Jürgen; Alpert, Gary (2002). "Gamergates in the myrmicine genusMetapone(Hymenoptera:Formicidae) ".Naturwissenschaften.89(7): 305–307.Bibcode:2002NW.....89..305H.doi:10.1007/s00114-002-0329-8.PMID12216860.S2CID6945541.
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