Ponera exotica

This species occurs in a variety of habitats, including mesic floodplain forests, dry upland forests, and prairies (Johnson 1987). Nests are small, typically with 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.

This species is distinguished from the other North American species of Ponera by its small size (length about 2 mm) and disproportionately large antennal club.

Distribution
North Carolina south into Florida, west into Oklahoma and southwestern Texas (Mackay and Anderson 1991). In Florida in occurs south into Highlands County. As its name implies, P. exotica was assumed to be introduced, primarily because of its apparent close relationship to Indo-Australian species (Smith 1962). The late date of the first specimens (1959) and its appearance following a huge amount of poorly regulated (from the standpoint of introduction of species) air traffic in the latter part of World War II also seem to have helped Marion Smith decide that this species is exotic. Robert Taylor, in his 1967 revision of Ponera, agreed that the species must be exotic, and evidently had discussed this with Marion Smith before the species was described. As a final, convincing bit of evidence, P. exotica is apparently so similar to the widely distributed, sometimes exotic species Ponera leae, not to be confused with Hypoponera lea, that Taylor (1967) wondered whether it could be a slight variant of that species. Clifford Johnson (1987), after considering the wide distribution of the species in undisturbed habitats, its absence from disturbed habitats, and the lack of any specimens from the Indo-Australian region, decided that the species is probably native. Its late discovery is not that unusual for a small, litter-inhabiting ant in southeastern North America. We provisionally accept this decision, assuming this to be an old genus with a relict distribution outside of the Indo-Australian region (like Cryptopone). There could easily be more species of tiny and cryptobiotic Ponera that await discovery to fill in the gaps between southern North America and the similar species on the other side of the globe.

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 - ).