Ponera exotica

A forest species that forms small nests, typically less than 60 workers.

Identification
Taylor (1967) - Exotica is similar to Ponera leae, from which it is distinguished by the characters in the species key. This couplet unequivocally separates all specimens studied here; its complexity reflects the close similarity between these species. exotica is easily distinguished from the sympatric Ponera pennsylvanica by its much smaller size, 4-segmented antennal club; lack of a mesometanotal suture, and much paler coloration.

Distribution
Mid and southwest US, Seychelles and Reunion.

The name of this species reflects Marion Smith's belief that it was imported from Asia, where there are related species. The distribution and habitat preferences of this species, however, suggest that it is native (Johnson 1987, MacKay and Anderson 1991). Its resemblance to Asian species might mean that this is an Arctotertiary relict lineage rather than a recent import. We provisionally consider this species to be native. (Deyrup, Davis & Cover, 2000.)

Distribution based on Regional Taxon Lists
Afrotropical Region: Comoros. Malagasy Region: Mayotte, Seychelles. Nearctic Region: United States.



Biology
Taylor (1967) - These records are all from Berlese funnel samples of leaflitter or leafmold. All except one (Beaufort Co., N. C., D. L. Wray) were gathered by Carter. The Beaufort Co. collection represents the first record of this species; it is dated September 1950. Carter's North Carolina records were made in June through early September 1960; the Oklahoma ones in July and August, 1963.

Conditions at each North Carolina collection site were reviewed in detail by M. R. Smith (1962). I quote here from Carter’s (1962b) summary of the ecology of this species in North Carolina.

“Specimens were collected in a xeric piedmont post oak — blackjack forest near Hillsboro and in a dry, sunny post oak — blackjack oak stand southeast of Charlotte. The coastal plain collections were obtained from well-shaded mesic forests of loblolly pine — hardwood — beech, loblolly pine, pine — dogwood, pine — hardwood, and oak — loblolly pine.”

It may be significant that higher elevation records on the piedmont plateau were from more xeric, less heavily shaded stations, with thinner leafmold and litter than the lower lying coastal plain sites. It would be interesting if an elevational shift in the ecological preferences could be demonstrated.

Carter gives the following descriptions of the Oklahoma stations (pers. Comm.). “Payne County is characterized by large areas of tall or mixed grass prairie with scrub oak forests on certain highland areas. These oak forests are quite xeric. Mesic forests of oaks and other hardwoods are found in stream floodplains and in deep ravines. All the Payne County collections were from mesic forests. The McCurtain County sites were also mesic in condition.”

Nomenclature

 *  exotica. Ponera exotica Smith, M.R. 1962b: 378, fig. 1 (w.q.) U.S.A. See also: Taylor, 1967a: 96; Johnson, C. 1987: 358.

Taylor (1967) - M. R. Smith (1962) noted the apparent relationship between exotica and the Indo-Australian Ponera species. He concluded that the exotica was probably introduced into the United States by man. These conclusions were based on his own studies, and on opinions ventured by the author (pers. comm.). I still subscribe to these views, though it would be desirable to see larvae of exotica. If they have 4 pairs of dorsal abdominal glutinous tubercles, as in pennsylvanica, I would assume them to be descended from the coarctata species group. If this is so, the resemblance between exotica and leae would represent an almost unbelievable case of convergent evolution.

Worker
Taylor (1967) - Little data additional to the original description is necessary, apart from the discussion of worker variation. The palpal formula of both queen castes is Maxillary 2: Labial 2 (3 Oklahoma workers and a queen dissected). Immature stages, males, and the queen wing venation are not known.

Type Material
Taylor (1967) - Croatan National Forest, North Carolina, United States (Holotype and Paratype examined - ).