Geographic Spread of Gnamptogenys triangularis ( Hymenoptera : Formicidae : Ectatomminae )

Gnamptogenys triangularis (Mayr), native to the forests of South and Central America, is a predatory ant that feeds on millipedes. In its native range, this species is known from Buenos Aires, Argentina (38.1◦S) in the south to Costa Rica (10.4◦N) in the north, with records from eight countries in South America (all except Chile, French Guiana, and Paraguay), and the two southernmost countries of Central America (Panama and Costa Rica). The first records of G. triangularis outside its native range came from Florida beginning in 1985 (six sites: 25.5◦–30.4◦N) and Alabama in 1996 (one site: 30.4◦N). Here we present the first records of G. triangularis from Mississippi, dating from 2002–2010 (five sites: 30.5◦–31.2◦N). Based on its South American range, it appears that G. triangularis has the potential to spread to forests throughout much of the southeastern USA. There are no documented impacts of G. triangularis, and it seems unlikely that this species will ever become a major pest.


Introduction
Gnamptogenys triangularis (Mayr), native to the forests of South and Central America, is a predatory ant that feeds on millipedes [1,2].Kusnezov [3] wrote that in Tucuman, Argentina, G. triangularis occurred by streams in the subtropical cloud forest areas.In Surinam, Kempf [4] recorded G. triangularis from a primary forest and a "marshy wood."Lattke et al. [5] wrote that G. triangularis nests in trees and broken branches lying on the forest floor in wet primary and secondary forests, from sea level to elevations >1,000 m.L. R. Davis collected specimens in Harrison County, Mississippi, nesting in a rotten pine limb in leaf litter beneath grape vines (from Mississippi Entomological Museum specimen label data).Other collections of this species in Mississippi were in deciduous forests.Lattke [1] reported that G. triangularis colonies typically have only 80-120 workers, up to a probable maximum of 150 workers.
The first records of G. triangularis outside its native range came from Miami-Dade County, Florida, beginning in 1985 [6,7].Deyrup [8] reported G. triangularis from two additional counties in Florida (Broward and Escambia).
MacGown and Forster [9] were the first to report this ant from Alabama (Mobile County).Here, we report the first records of G. triangularis from Mississippi and evaluate its potential spread based on its known native range.
Gnamptogenys triangularis and Gnamptogenys hartmani (Wheeler) are the only two members of the subfamily Ectatomminae known to occur in the southeastern USA.These very distinctive ants can be recognized immediately by the deep horizontal grooves covering the entire head and body.Gnamptogenys triangularis workers are ∼5.0 mm in length and dark brown (Figure 1(a)).Females are similar in appearance to workers, but are slightly larger (∼5.5 mm in length) and have brownish gray colored wings (Figure 1(b)).In comparison, Gnamptogenys hartmani workers are 3.5-4.0mm and pale reddish brown.Females are ∼5 mm and similar in appearance to workers.Males are approximately the same size as females, but horizontal grooves are greatly reduced, and overall they are shinier in appearance.The entire body is reddish brown, legs and scapes are yellowish brown, and the funiculus is dark colored.

Methods
Using published and unpublished records, we documented the native and exotic range of G. triangularis.We obtained unpublished site records from museum specimens in the collections of the Museum of Comparative Zoology (MCZ, identified by S. Cover) and the Smithsonian Institution (SI, identified by M. Smith).In addition, we used online databases with collection information on specimens by Antweb (http://www.antweb.org/)and the Global Biodiversity Information Facility (http://www.gbif.org/).

Results
In South and Central America, G. triangularis has been recorded from 12 countries (Table 1) from central Argentina to Costa Rica (Figure 2).References to this species occurring in French Guiana appear to be the type locale of G. aculeaticoxae (G.triangularis), nowin Brazil (see Section 1).Published records of G. triangularis outside its native range come from Florida beginning in 1985 (four sites: 25.5 • -30.

Discussion
Records of G. triangularis come from eight countries in South America (all except Chile, French Guiana, and Paraguay), and the two southernmost countries of Central America (Panama and Costa Rica) (Figure 2, Table 1).Because there are no discernable geographic barriers, it seems very likely that the native range of G. triangularis also extends into forest habitats in French Guiana, Paraguay, and farther  2).Based on its South American range, extending to 38.1 • S, it is possible that G. triangularis could spread to forests throughout much of the southeastern USA, perhaps as far north as Richmond, Virginia (37.5 • N) and Lexington, Kentucky (38.0 • N).
Many of the Mississippi records are based on specimens collected in Malaise traps.These traps and other flight interception traps may be useful methods for monitoring the movements of exotic species, especially alate males and females.
In both its native and exotic ranges, G. triangularis inhabits forests and preys on millipedes [2,3,8].There are no known impacts of G. triangularis, even though if this species was having a localized impact on millipede populations, it seems unlikely that this would have been detected.Nonetheless, it seems unlikely that this species will ever become a major pest.

Table 1 :
Earliest known records for Gnamptogenys triangularis from South and Central America.MCZ: Museum of Comparative Zoology.