Azteca

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Azteca
Azteca alfari (Photo April Nobile, www.antweb.org)

Azteca alfari (Photo April Nobile, www.antweb.org)

Systematics
Class : Insects (Insecta)
Order : Hymenoptera (Hymenoptera)
Family : Ants (Formicidae)
Subfamily : Glandular Ants (Dolichoderinae)
Genre : Azteca
Scientific name
Azteca
Forel , 1878

Azteca is a genus of ants (Formicidae) from the subfamily of gland ants (Dolichoderinae), which occurs with around 90 species in Central and South America ( Neotropis ), north to central Mexico. It isthe second largest genus of the subfamilyafter Dolichoderus . They are often among the most common ants in the tropical lowlands.

features

All species of the genus Azteca have two different worker morphs, which differ markedly in body size. The species of the genus have a poorly armored, thin cuticle , the surface of which is unsculptured; mostly it is either weakly spotted or has tiny dimples. Larger elements such as thorns, spines, keels or ribs never appear. The head of the animals is more or less indented at the apex and therefore somewhat heart-shaped, especially in the larger workers. He wears round complex eyes, which sit relatively far in front of the head, and in the larger workers (majores) also point eyes ( ocellen ). The mandibles have a chewing bar with 7 to 9 teeth, the outermost of which is not enlarged. The clypeus is drawn forward at the anterior corners on the outside (anterolateral). The petiolus has a distinctive scale that is rounded towards the front and is also widened in a knot-shaped manner downwards. A clear incision between the mesonotum and propodeum can be seen on the fuselage through a pit on the metanotum . The workers of the different species are quite variable within the species (intraspecific) and quite similar between the species (interspecific), so that they are difficult to identify as workers.

Way of life

All Azteca species nest on trees ( arboricol ). Many species build cardboard nests from chewed plant fibers, either free or in cavities such as tree hollows or hollow stems; these gain additional strength through the growing fungal mycelium. Others nest directly in the cavities of plants, many species in those that are provided by certain tree species specifically for this purpose (so-called domatia ). Few species, for example the Azteca trailii found in Brazil , create so-called ant gardens in their cardboard nests ; To do this, they bring in seeds from epiphytic plant species that germinate here and form a special micro-ecosystem ( synusia ). Some Azteca TYPES feed as unspecialized predators ( predators ) of small arthropods , but many species are symbiotic received relationships with other organisms that are essential to their diet. For example, some species of scale insects of the families Coccidae and Pseudococcidae breed and feed on their excretions. Others are nourished by certain tree species in exchange for herbivore protection.

Azteca species are usually rich in individuals in their habitats. They are usually dominant over other ant species that occur in the same habitat. They are not very sensitive to human influences. In disturbed and secondary forests, they are often even more common than in undisturbed rainforests.

Symbiosis with ant trees

Some species of this genus, in particular Azteca constructor , Azteca muelleri , Azteca xanthochroa , Azteca coeruleipennis , Azteca alfari and Azteca ovaticeps , are characterized by a remarkable symbiosis with plants of the genus Cecropia , the so-called ant trees ; this is sometimes referred to as myrmecophylaxis . These trees are particularly widespread in tropical secondary forests , for example after slash and burn. More than half of the trees (between 47 and 85 percent) have their own ant colony. The young queens compete for suitable trees and do not allow any further colony in the same cavity (internode). Usually there is only one successful ant colony per tree. Numerous other ant species try to form colonies on Cecropia , but these are usually inferior to Azteca in the competition . However, some species of the genera Pachycondyla and Camponotus also colonize older Cecropia trees.

The ants live in the internodes , the hollow twigs and trunks divided by transverse walls between the leaf bases, in which they create cardboard nests. The internodes are stiffened on the outside by a hard sclerenchyme , while the inside is initially filled with a soft marrow. On older sprouts, the pulp recedes and releases cavities for the ants to colonize. On the outside, the plant forms a thin, preformed zone without the latex ducts otherwise used for defense , which is called a prostoma; it makes it easier for the queen ants to enter. The hole cleared here later serves as the first exit for the ant colony. Older colonies gnaw holes through the septa between the internodes and have numerous exit holes all over the plant.

The ants are also supplied with food by the plants. To the form on the outside of the base petiole at the top of leaf hairs ( trichomes ) in protein and fat, so-called "Muller's corpuscles" (named after the discoverer of this symbiosis, Fritz Müller ), mainly the larvae as Serve food. In addition, the ants eat honeydew from scale insects . In return, they defend these plants against pests and predators, they even fight growing epiphytes and lianas . Some of the animals are extremely aggressive towards any approach to their tree, including vertebrates and humans. They are even able to defend themselves against the driver ants of the genus Eciton , which ignore trees with Azteca colonies on their raids.

Advantages and disadvantages for the symbiotic partners

The ants receive living space and food, but they have to accept that they are exposed to an increased risk of woodpecker attacks, which they can eat on the trunks much more easily than ants living on the ground. Queens and young ant colonies also suffer high losses due to the aggressiveness of the established colonies, which is directed against them as possible competitors as well as against the plant pests.

The trees have to use energy to feed the ants. In addition, they are more damaged by woodpeckers than other trees and have to accept losses from the scale insects that the ants tend and defend. To do this, they protect the ants from other pests as well as from climbing plants and epiphytes . The trees also benefit from the nitrogen-rich excretions of the ants.

A modeling of the symbiosis revealed that the mutual benefits outweigh the drawbacks well. However, young trees benefit more from the connection than older specimens.

evolution

The genus Azteca is relatively basal in the subfamily Dolichoderinae according to morphological characteristics. In Dominican amber from the Miocene , the species Azteca alpha is the most common fossil . Workers were found in direct contact with scale insects; this suggests that this symbiosis has existed for 15 to 20 million years. An examination of the relationships within the genus Azteca based on the comparison of sequences of the MtDNA showed that the species that enter into a symbiosis with Cecropia are not closely related to one another. Accordingly, this symbiosis has arisen several times independently of one another.

Individual evidence

  1. ↑ Azteca in AntWeb
  2. ^ A b John T. Longino: A taxonomic review of the genus Azteca (Hymenoptera: Formicidae) in Costa Rica and a global revision of the aurita group. Zootaxa 1491: (2007) pp. 1-63.
  3. ↑ Steven O. Shattuck: Generic Revision of the Ant Subfamily Dolichoderinae (Hymenoptera, Formicidae). In: Sociobiology. Volume 21, No. 2: (1992) pp. 1-177.
  4. ↑ Veronika E. Mayer, Hermann Voglmayr: Mycelial carton galleries of Azteca brevis (Formicidae) as a multi-species network. In: Proceedings of the Royal Society London Series B 276: (2009) pp. 3265-3273 doi: 10.1098 / rspb.2009.0768 .
  5. ↑ Jérôme Orivel, Celine Leroy: The diversity and ecology of ant gardens (Hymenoptera: Formicidae; Spermatophyta: Angiospermae). In: Myrmecological News. 14: (2011) pp. 73-85.
  6. ↑ Stacy M. Philpott, Ivette Perfecto, Inge Armbrecht, Catherine L. Parr: Ant Diversity and Function in Disturbed and Changing Habitats. In: Lori Lach, Catherine L. Parr, Kirsti L. Abbott (Eds.): Ant Ecology. Oxford University Press, 2009, ISBN 978-0-19-954463-9 .
  7. ↑ Kari T. Ryder Wilkie, Amy L. Mertl, James FA Traniello: Diversity of ground-dwelling ants (Hymenoptera, Formicidae) in orginary and secondary forests in Amazonian Ecuador. In: Myrmecological News. 12: (2009) pp. 139-147.
  8. ^ John T. Longino: Azteca ants in Cecropia trees: taxonomy, colony structure and behavior. In: CR Huxley, DF Cutler (Ed.): Ant-Plant-Interactions. Oxford University Press, 1991, pp. 271-288.
  9. ^ A b c d David Logue: The Costs and Benefits of the Cecropia-Azteca-Coccidae Symbiosis. Archived from the original on May 20, 2008 ; Retrieved February 24, 2013 .
  10. ↑ Alain Dejean, Bruno Corbara, Olivier Roux, Jerome Orivel: The antipredator behavior of Neotropical ants toward army ant raids. (Hymenoptera, Formicidae). In: Myrmecological News. 19: (2013) pp. 17-24.
  11. ↑ Steven O. Shattuck: Generic-level relationships within the ant subfamily Dolichoderinae (Hymenoptera: Formicidae). In: Systematic Entomology. 20: (1995) pp. 217-228.
  12. ↑ Christine Johnson, Donat Agosti, Jaques H. Delabie, Klaus Dumpert, DJ Williams, Michael von Tschirnhaus, Ulrich Maschwitz : Acropyga and Azteca Ants (Hymenoptera: Formicidae) with Scale Insects (Sternorrhyncha: Coccoidea): 20 Million Years of Intimate Symbiosis. In: American Museum Novitates. No. 3335. (2001) 21 pp.
  13. ^ Francisco Jose Ayala, James K. Wetterer, John T. Longino, Daniel L. Hartl: Molecular Phylogeny of Azteca Ants (Hymenoptera: Formicidae) and the Colonization of Cecropia Trees. In: Molecular Phylogenetics and Evolution. Volume 5, No. 2: (1996) pp. 423-428.

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