Acromyrmex echinatior

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Acromyrmex echinatior
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Myrmicinae
Tribe: Attini
Genus: Acromyrmex
Species: A. echinatior
Binomial name
Acromyrmex echinatior
(Forel, 1899)

Acromyrmex echinatior casent0909421 p 1 high.jpg

Acromyrmex echinatior casent0909421 d 1 high.jpg

Specimen Labels

Acromyrmex echinatior is a host species of the social parasite Acromyrmex insinuator.

Identification

Schultz et al. (1998) - Acromyrmex octospinosus var. echinatior was described by Forel (1900) and elevated to subspecies status by Wheeler (1937). These authors, as well as Santschi (1925), recognized A. octospinosus echinatior principally by the sculpture of the head and gaster of the major worker: “the tubercles on the posterior corners of the head, the pedicel, and the gaster are more developed and subspiniform, and some of those on the sides of the head are distinctly curved forward” (Wheeler, 1937).

WORKERS: In the fifty nests excavated in Panama, the largest major workers of A. echinatior are the same size as those of Acromyrmex octospinosus. However, a previous study by Bot and Boomsma (1997) found that pronotum width in A. echinatior (species 1 in that study) was significantly smaller than pronotum width in A. octospinosus (species 2 in that study). Qualitatively, major workers of the two species differ in the following ways: In A. echinatior the lateral pronotal spines are nearly vertical and parallel in frontal view, the vertical angle noticeably different from the angle of the anterior mesonotal spines, which diverge. In A. octospinosus, the anterior spines are not vertical and both pairs of spines diverge at approximately the same angle. Major workers of A. echinatior are hairier than those of A. octospinosus; e. g., at least some setae are present on the face of the propodeal dorsum in addition to those associated with the propodeal spines and with the anterior tubercles, whereas in A. octospinosus such setae are absent. In general, tubercles on the gaster of A. echinatior workers are sharp and dentiform to subspiniform, whereas those in A. octospinosus are low and blunted. Likewise, tubercles on the head of A. echinatior are sharp and spiniform, whereas those of A. octospinosus are shorter and blunter. We caution, however, that there is overlap between the two species in the form of the spines of the gaster and head and that these commonly cited characters are therefore not entirely reliable. Worker color is quite variable, ranging from yellow in callows to yellowish-ferrugineous to ferrugineous, with, as noted by Wheeler (1937) some workers acquiring a “bluish bloom.”

When workers from the entire range of both species are taken into account, the most constant distinguishing characters are the form of the spines on the head and gaster and to a lesser extent the differing angles of the lateral pronotal vs. anterior mesonotal spines. Major workers of A. echinatior from Costa Rica, Nicaragua, Guatemala, and Mexico, including the lectotype, frequently lack setae on the propodeal dorsum and are often much larger than those from the Panamanian nests.

FEMALES: In the Panamanian nests, A. echinatior females are smaller than Acromyrmex octospinosus females, and differ from them in the presence of a pigment spot entirely surrounding the ocelli (absent in the Panamanian A. octospinosus), the presence of setae on the propodeal dorsum (absent in A. octospinosus), and the presence of a broadly convex median anteroventral postpetiolar extension (variable in A. octospinosus). The occipital tubercle is thin and sharp and the tubercles on the first gastric tergite are sharp and dentiform; in A. octospinosus the occipital tubercle is thick and blunt, and the gastric tubercles are blunt and rounded. Color variation in females corresponds to that in workers. Over the whole of the species’ Central American range, A. echinatior females are more variable in size than in the Panamanian sample, tending to be larger, and variable in the presence/absence of the ocellar pigment spot.

MALES: In the Panamanian nests, A. echinatior males are the same size as A. octospinosus males, but differ from them by the presence of a pigmented frontal triangle that is entirely delineated by rugae (unpigmented and ill-defined in A. octospinosus), the presence of setae on the propodeal dorsum (absent in A. octospinosus), and the presence of a broadly convex median anteroventral postpetiolar extension (variable in A. octospinosus). Color is yellow-ferrugineous. A. echinatior males over the rest of the species’ range are variable in the characters of the frontal triangle.

Assigning the Panamanian specimens to A. echinatior is not without problems. The largest Panamanian workers are smaller than the lectotype and smaller than other worker specimens from Costa Rica, Nicaragua, Guatemala, and Mexico. Differences also exist in the characters of the propodeal setae (all castes), the ocellar pigment spot in females, and the form of the frontal triangle in males. Although the conservative position taken here is that these differences fall within the normal range of variation expected from a species distributed over a wide area, we would not be at all surprised to find that both Acromyrmex octospinosus sensu lato and Acromyrmex echinatior are composed of a number of cryptic species. If this is established by future research, then the Panamanian host of Acromyrmex insinuator may require species status separate from A. echinatior.

Distribution

Latitudinal Distribution Pattern

Latitudinal Range: 18.62° to 8.808°.

 
North
Temperate 		North
Subtropical 		Tropical South
Subtropical 		South
Temperate

Distribution based on Regional Taxon Lists

Neotropical Region: Costa Rica, El Salvador, Guatemala, Honduras, Mexico (type locality), Nicaragua, Panama.

Distribution based on AntMaps

AntMapLegend.png

Distribution based on AntWeb specimens

Check data from AntWeb

Countries Occupied

Number of countries occupied by this species based on AntWiki Regional Taxon Lists. In general, fewer countries occupied indicates a narrower range, while more countries indicates a more widespread species.
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Estimated Abundance

Relative abundance based on number of AntMaps records per species (this species within the purple bar). Fewer records (to the left) indicates a less abundant/encountered species while more records (to the right) indicates more abundant/encountered species.
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Biology

Explore-icon.png Explore Fungus Growing 
For additional details see Fungus growing ants.

A handful of ant species (approx. 275 out of the known 15,000 species) have developed the ability to cultivate fungus within their nests. In most species the fungus is used as the sole food source for the larvae and is an important resource for the adults as well. Additionally, in a limited number of cases, the fungus is used to construct part of the nest structure but is not as a food source.

These fungus-feeding species are limited to North and South America, extending from the pine barrens of New Jersey, United States, in the north (Trachymyrmex septentrionalis) to the cold deserts in Argentina in the south (several species of Acromyrmex). Species that use fungi in nest construction are known from Europe and Africa (a few species in the genera Crematogaster, Lasius).


The details of fungal cultivation are rich and complex. First, a wide variety of materials are used as substrate for fungus cultivating. The so-called lower genera include species that prefer dead vegetation, seeds, flowers, fruits, insect corpses, and feces, which are collected in the vicinity of their nests. The higher genera include non leaf-cutting species that collect mostly fallen leaflets, fruit, and flowers, as well as the leafcutters that collect fresh leaves from shrubs and trees. Second, while the majority of fungi that are farmed by fungus-feeding ants belong to the family Lepiotaceae, mostly the genera Leucoagaricus and Leucocoprinus, other fungi are also involved. Some species utilise fungi in the family Tricholomataceae while a few others cultivate yeast. The fungi used by the higher genera no longer produce spores. Their fungi produce nutritious and swollen hyphal tips (gongylidia) that grow in bundles called staphylae, to specifically feed the ants. Finally, colony size varies tremendously among these ants. Lower taxa mostly live in inconspicuous nests with 100–1000 individuals and relatively small fungus gardens. Higher taxa, in contrast, live in colonies made of 5–10 million ants that live and work within hundreds of interconnected fungus-bearing chambers in huge subterranean nests. Some colonies are so large, they can be seen from satellite photos, measuring up to 600 m3.

Based on these habits, and taking phylogenetic information into consideration, these ants can be divided into six biologically distinct agricultural systems (with a list of genera involved in each category):

Nest Construction

A limited number of species that use fungi in the construction of their nests.

Lower Agriculture

Practiced by species in the majority of fungus-feeding genera, including those thought to retain more primitive features, which cultivate a wide range of fungal species in the tribe Leucocoprineae.

Coral Fungus Agriculture

Practiced by species in the Apterostigma pilosum species-group, which cultivate fungi within the Pterulaceae.

Yeast Agriculture

Practiced by species within the Cyphomyrmex rimosus species-group, which cultivate a distinct clade of leucocoprineaceous fungi derived from the lower attine fungi.

Generalized Higher Agriculture

Practiced by species in several genera of non-leaf-cutting "higher attine" ants, which cultivate a distinct clade of leucocoprineaceous fungi separately derived from the lower attine fungi.

Leaf-Cutter Agriculture

A subdivision of higher attine agriculture practiced by species within several ecologically dominant genera, which cultivate a single highly derived species of higher attine fungus.

Note that the farming habits of Mycetagroicus (4 species) are unknown. Also, while species of Pseudoatta (2 species) are closely related to the fungus-feeding genus Acromyrmex, they are social parasites, living in the nests of their hosts and are not actively involved in fungus growing. ‎

Nehring et al. (2015) - This species and the sympatric Acromyrmex octospinosus are both parasitized by Acromyrmex insinuator but the parasitic queens are only able to successfully reproduce in A. echinatior nests.

Reproduction

Liberti et al. (2018) studied sperm competition in this species. Queens of A. echinatior mate with multiple males. An earlier study (Liberti et al. 2016) found that queens produce reproductive tract fluid that enhances sperm motility. This increases the possibility that the subsequently stored sperm is viable. This current study found sperm motility increased when exposed to other male ejaculates. This increased activity was similar to what was observed with exposure to reproductive tract fluid in queens. Liberti et al. concluded "Our results suggest that ant sperm respond via a self–non-self recognition mechanism to similar or shared molecules expressed in the reproductive secretions of both sexes. Lower sperm motility in the presence of own seminal fluid indicates that enhanced motility is costly and may trade-off with sperm viability during sperm storage, consistent with studies in vertebrates. Our results imply that ant spermatozoa have evolved to adjust their energetic expenditure during insemination depending on the perceived level of sperm competition."

Genetics

Acromyrmex echinatior has had their entire genome sequenced.

Palomeque et al. (2015) found class II mariner elements, a form of transposable elements, in the genome of this ant.

Association with Other Organisms

Explore-icon.png Explore: Show all Associate data or Search these data. See also a list of all data tables or learn how data is managed.
  • This species is a host for the fungus Aspergillus flavus (a parasitoid) (Quevillon, 2018) (encounter mode primary; direct transmission; transmission within nest).

Castes

Worker

Images from AntWeb

Acromyrmex echinatior casent0909422 h 1 high.jpgAcromyrmex echinatior casent0909422 d 1 high.jpgAcromyrmex echinatior casent0909422 p 1 high.jpgAcromyrmex echinatior casent0909422 l 1 high.jpg
Paralectotype of Acromyrmex echinatior. Worker. Specimen code casent0909422. Photographer Will Ericson, uploaded by California Academy of Sciences. Owned by MHNG, Geneva, Switzerland.

Nomenclature

The following information is derived from Barry Bolton's Online Catalogue of the Ants of the World.

  • echinatior. Atta (Acromyrmex) octospinosa var. echinatior Forel, 1899c: 34 (w.q.) MEXICO (Chihuahua), GUATEMALA, COSTA RICA, PANAMA.
    • Wheeler, W.M. 1937c: 72 (m.).
    • Combination in Acromyrmex: Emery, 1924d: 350.
    • Junior synonym of octospinosus: Emery, 1905c: 44.
    • Subspecies of octospinosus: Forel, 1912e: 181; Emery, 1924d: 350; Santschi, 1925a: 391 (in key); Wheeler, W.M. 1937c: 71; Wheeler, W.M. 1938: 252; Santschi, 1939e: 319 (in key); Santschi, 1939f: 166 (in key); Weber, 1941b: 125; Kempf, 1972a: 14; Bolton, 1995b: 55.
    • Status as species: Schultz, Bekkevold & Boomsma, 1998: 460; Branstetter & Sáenz, 2012: 257.

Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.

Type Material

Schultz et al. (1998) - LECTOTYPE: Major worker. Guatemala: Senahuen Vera Paz, El Reposo, Zapote, 800 ft. (Champion). A. Forel Collection, Muséum d’Histoire naturelle, Geneva, Switzerland. Paratypes examined: 2 minor workers: Guatemala: Senahuen Vera Paz, El Reposo, 800 ft. (Champion). 1 alate and 1 dealate female: Panama: Volcan de Chiriquí, 25–1000 ft. (Champion). 2 alate females: Panama: Bugaba (Champion).

The list of specimens published in Forel’s (1899) description includes two workers, one from Guatemala and one from Costa Rica, the latter now apparently lost. Forel (1899) did not designate a holotype; five pins (seven specimens) in the syntype series bear the designation “type” written in Forel’s hand. Affixed to two of Forel’s syntype pins, one bearing a single major worker, the other bearing two females, are red “Typus” labels, but these may have been added subsequently and at any rate have no formal standing. Wheeler (1937) designated the type locality of A. octospinosus echinatior as Volcan de Chiriquí, Panama, the collection locality of two of Forel’s syntype females, but did not designate a lectotype. We have chosen to ignore this action and to designate the only remaining major worker in Forel’s syntype series as the lectotype for two important reasons: (1) species concepts in Acromyrmex are based entirely upon the characters of major workers and (2) Forel’s syntype females vary in size and collection locality, raising the possibility that they represent multiple species.

Description

Worker

Schultz et al. (1998) - LECTOTYPE: HL = 2.16; HW = 2.64; WL = 3.72; SL = 2.64; maximum diameter of eye = 0.43.

Karyotype

  • 2n = 38, karyotype = 8M+6SM+14ST+10A (Brazil) (Barros et al., 2016).

References

References based on Global Ant Biodiversity Informatics

  • Ahuatzin D. A., E. J. Corro, A. Aguirre Jaimes, J. E. Valenzuela Gonzalez, R. Machado Feitosa, M. Cezar Ribeiro, J. Carlos Lopez Acosta, R. Coates, W. Dattilo. 2019. Forest cover drives leaf litter ant diversity in primary rainforest remnants within human-modified tropical landscapes. Biodiversity and Conservation 28(5): 1091-1107.
  • Bekkevold, D., J. Frydenberg and J.J. Boomsma. 1999. Multiple mating and facultative polygyny in the Panamanian leafcutter ant Acromyrmex echinatior. Behavioral Ecology and Sociobiology 46:103-109.
  • Dattilo W. et al. 2019. MEXICO ANTS: incidence and abundance along the Nearctic-Neotropical interface. Ecology https://doi.org/10.1002/ecy.2944
  • Fernandes, P.R. XXXX. Los hormigas del suelo en Mexico: Diversidad, distribucion e importancia (Hymenoptera: Formicidae).
  • Fernández, F. and S. Sendoya. 2004. Lista de las hormigas neotropicales. Biota Colombiana Volume 5, Number 1.
  • Forel A. 1912. Formicides néotropiques. Part II. 3me sous-famille Myrmicinae Lep. (Attini, Dacetii, Cryptocerini). Mémoires de la Société Entomologique de Belgique. 19: 179-209.
  • Kempf, W.W. 1972. Catalago abreviado das formigas da regiao Neotropical (Hym. Formicidae) Studia Entomologica 15(1-4).
  • Kooij P. W., B. M. Dentinger, D. A. Donoso, J. Z. Shik, and E. Gaya. 2018. Cryptic diversity in Colombian edible leaf-cutting ants (Hymenoptera: Formicidae). Insects 9: 191.
  • Longino J. T. 2013. Ants of Nicargua. Consulted on 18 Jan 2013. https://sites.google.com/site/longinollama/reports/ants-of-nicaragua
  • Longino J. et al. ADMAC project. Accessed on March 24th 2017 at https://sites.google.com/site/admacsite/
  • Longino, J.T. 2010. Personal Communication. Longino Collection Database
  • Maes, J.-M. and W.P. MacKay. 1993. Catalogo de las hormigas (Hymenoptera: Formicidae) de Nicaragua. Revista Nicaraguense de Entomologia 23.
  • Philpott, S.M., P. Bichier, R. Rice, and R. Greenberg. 2007. Field testing ecological and economic benefits of coffee certification programs. Conservation Biology 21: 975-985.
  • Poulsen, M., W.O.H. Hughes and J.J. Boomsma. 2006. Differential resistance and the importance of antibiotic production in Acromyrmex echinatior leaf-cutting ant castes towards the entomopathogenic fungus Aspergillus nomius. Insectes Sociaux 53:349-355
  • Schultz T. R., D. Bekkevold, J. J. Boomsma. 1998. Acromyrmex insinuator new species; an incipient social parasite of fungus-growing ants. Insectes Soc. 45(4): 457-471.
  • Solomon S. E., C. Rabeling, J. Sosa-Calvo, C. Lopes, A. Rodrigues, H. L. Vasconcelos, M. Bacci, U. G. Mueller, and T. R. Schultz. 2019. The molecular phylogenetics of Trachymyrmex Forel ants and their fungal cultivars provide insights into the origin and coevolutionary history of ‘higher-attine’ ant agriculture. Systematic Entomology 44: 939–956.
  • Sumner, S., D.K. Aanen, J. Delabie and J.J. Boomsma. 2004. The evolution of social parasitism inAcromyrmexleaf-cutting ants: a test of Emery’s rule. Insectes Sociaux 51(1):37-42.
  • Sumner, S., W.O.H. Hughes and J.J. Boomsma. 2003. Evidence for Differential Selection and Potential Adaptive Evolution in the Worker Caste of an Inquiline Social Parasite. Behavioral Ecology and Sociobiology 54(3):256-263
  • Vásquez-Bolaños M. 2011. Lista de especies de hormigas (Hymenoptera: Formicidae) para México. Dugesiana 18: 95-133
  • Weber N. A. 1941. The biology of the fungus-growing ants. Part VII. The Barro Colorado Island, Canal Zone, species. Rev. Entomol. (Rio J.) 12: 93-130.
  • Wheeler W. M. 1937. Mosaics and other anomalies among ants. Cambridge, Mass.: Harvard University Press, 95 pp.
  • Zelikova, T.J. and M.D. Breed. 2008. Effects of habitat disturbance on ant community composition and seed dispersal by ants in a tropical dry forest in Costa Rica. Journal of Tropical Ecology 24:309-316
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