Pogonomyrmex

SEM image of P. barbatus (Picture: C.-P. Strehl)

Pogonomyrmex is a genus of ants ( Formicidae ), and belongs to the subfamily of red ants ( Myrmicinae ).

We know about 60 known species, which are common in deserts and steppe regions of the New World (North, Central and South America) and can be split into at least two sub- genres: Pogonomyrmex sensu stricto (G. Mayr, 1868) and Ephebomyrmex (WM Wheeler, 1902). The name of the genus comes from the Greek and refers to a beard -like ( gr Pogon = beard) structure below the head in most representatives of the subgenus sensu stricto, the Psammophore (see picture: Pogonomyrmex barbatus). This structure lacks the representatives of the subgenus Ephebomyrmex whose name was derived from the Greek name for a beardless youth ( ephebos ), and generally has smaller individuals and colonies.

Evolution

The first Pogonomyrmex species originated within the subfamily Myrmicinae probably before about 30 million years ago in the dry phase of the Oligocene, and the first grasses. As the closely related genera are Myrmica and Hylomyrma.

Nutrition

Pogonomyrmex species feed on occasionally captured insects or other animals. The main food source for the colonies, however, provide seeds represent, which are usually collected from grasses of the environment and can be stored ( up to 2m deep) as storage in underground food storage. Members of this genus, therefore, belong to the so-called harvesting ants. The grinding of the hard seed coats is facilitated in most Pogonomyrmex species by the presence of strong mandible muscles, giving them a distinctive, beefy head.

Toxicity

Workers and queens have a sting that can be used multiple times and can also pierce human skin. Males are spineless. The engraving of the representatives of the most Pogonomyrmex species is painful for people. The type Pogonomyrmex maricopa is one of the species with the lowest ever measured in mice lethal dose (LD50 ) of insecticide. The strength of the poison may serve the defense of the underground seed stores from gerbils. Lizards of the genus Phrynosoma, however, are immune to the poison and one of the main predators. The venom of some Pogonomyrmex species was by some North American Indians as a hallucinogenic, ie the perception altering agent used.

Intra -colonial relationship

The mating behavior of the monogynous North American P. sensu stricto species was well by Bert Hölldobler studied in the 1970s. It can be found in P. sensu stricto species for eusoziale Hymenoptera unusually high mating frequencies of queens, which should cause the offspring of a queen in a colony of several fathers, and thus to each other have a low degree of relationship (see also: kin selection ). For Pogonomyrmex occidentalis these high mating frequencies of queens of Blaine J. Cole and Diane C. Wiernasz were detected in 1999 by means of genetic fingerprint for the first time. Since then, multiple pairing could also in many other sensu stricto species are detected genetically (eg for P. badius, P. barbatus, P. rugosus ). Cole and Wiernasz showed for P. occidentalis also that the resulting by the multiple mating of queens lower affinity correlates among nestmates with a faster growth of the entire colony. Possible explanation of the two scientists: the lower intra colonial relationship causes a higher genetic variability, which in Pogonomyrmex ( a) a better defense against parasites or ( b ) in turn allows for a more efficient working performance of the entire colony.

A multiple mating has been demonstrated only for representatives of the subgenus sensu stricto, for the subgenus Ephebomyrmex however, have not. However, the genetic variability of the colonies appeared to increase in Ephebomyrmex species, as several queens can lay eggs (functional polygyny ).