Tetramorium lucayanum Wheeler, described from the Bahamas, was long thought to be of West Indian origin. This species, however, is actually originally from Africa, and has been transported to the West Indies and elsewhere through human commerce. To examine the worldwide spread of T. lucayanum, I compiled and mapped specimen records from > 75 sites. I documented the earliest known T. lucayanum records for 22 geographic areas (countries and West Indies Islands), including 3 for which I found no previously published records: Gambia, Tortola, and Vieques. Tetramorium lucayanum has widely scattered records from 12 tropical African countries, primarily from forested sites. Exotic records of T. lucayanum come from 7 West Indies islands, Brazil, and greenhouses in Ireland and Italy. All outdoor records of T. lucayanum are from tropical sites, except for 2 subtropical records, both from urban Nassau, the capital of the Bahamas (25.1 °N): the original type locale and my new record from the local zoo, 2.5 km to the west. Most exotic records come from Cuba and Jamaica, but even on these islands T. lucayanum appears to be fairly rare and with no discernable ecological impact.
Tramp ants associate with human disturbance and disperse around the world through human commerce. Many tramp ant species began to spread outside their native range centuries ago, and were first described from specimens collected in non-native locales. For example, Monomorium pharaonis (L.), Paratrechina longicornis (Latreille), Tapinoma melanocephalum (F.), and Tetramorium bicarinatum Nylander are all tramp species originally from Asia, but they were first described from Egypt, Senegal, French Guiana, and California, respectively (Wetterer 2008, 2009a,b, 2010b). Here, I examine the geographic spread of Tetramorium lucayanum, an African species described from the Bahamas and long thought to be native to the West Indies.
Taxonomy and Origin
Wheeler (1905) described T. lucayanum from “two workers found running on the ground in the Queen's Staircase at Nassau” on the island of New Providence, Bahamas. Wheeler (1905) named the species after the Lucayan people, the inhabitants of the Bahamas when Europeans arrived, who called themselves Lukku-Cairi (meaning “island people”). Over the following decades, T. lucayanum was reported from several other West Indies islands: Cuba (Mann 1920), Jamaica (Aguayo 1932), Puerto Rico (Smith 1936), and St. Croix (Beatty 1944).
Smith (1936) wrote that on Puerto Rico “T. lucayanum is probably the only species of the genus that is native to the island.” Brown (1957), however, noted the similarity of T. lucayanum to African species. Brown (1964) recounted his search for museum specimens of T. lucayanum from Africa: “In my 1957 paper (p. 6), I stated my opinion that T. lucayanum, despite its wide distribution in the West Indies, must be a post-Columbian immigrant to the New World, and that it most likely came from Africa. Repeated attempts to match its types with Old World Tetramorium species represented in American museum collections all led to failure; though T. lucayanum did seem to be more or less closely related to certain African Tetramorium, it was apparently not conspecific with any available samples from the Old World. In 1963, when I had an opportunity to visit the classical European ant collections, I took along digms of T. lucayanum (from Jamaica) in the hope that I would be able to make their match. I am pleased to report that the search was successful.” Brown (1964) concluded that 3 Old World taxa were all junior synonyms of T. lucayanum: T. camerunense waelbroeki from Zaire (spelled waelbroecki by Santschi 1914 and Bernard 1952), T. lucayanum sexdens from a greenhouse at a botanical garden in Ireland (Forel 1915), and T. rectinodis from Equatorial Guinea (Menozzi 1942). Brown (1964) also reported additional African specimens of T. lucayanum, from Ivory Coast and Liberia. Brown (1964) wrote: “It may be that the West Indies stock arrived in ballast or timber, or perhaps with the slave trade, in a ship from Africa in the early days of New World colonization. At any rate, it is now clear that Africa was its original home.” McGlynn (1999) listed T. lucayanum as a native of the West Indies, citing Delabie (1994). Delabie (1994), however, wrote that T. lucayanum was a native of Central and West Africa, citing Brown (1964).
Tetramorium lucayanum workers are medium size (∼3 mm length) with a shiny dark brown to black body and head, which contrast with its light brown appendages. Because T. lucayanum is not originally from the Bahamas as its Latin name implies, I propose “ebony ant” as a common name for this species, based on its dark color and its Old World origin, like the wood of ebony trees (Diospyros spp.).
MATERIALS AND METHODS
Using published and unpublished records, I documented the worldwide range of T. lucayanum. I obtained unpublished site records from museum specimens in the collection of the Museum of Comparative Zoology (MCZ, identified by S. Cover) and the Natural History Museum, London (BMNH, identified by B. Bolton; collection data recorded by F. Hita Garcia). In addition, I used on-line databases with collection information on specimens by Antweb ( www.antweb.org) and the Global Biodiversity Information Facility ( www.gbif.org). I received unpublished record information from F. Hita Garcia (Kenya), J. Delabie (Brazil), and A. Dejean (Cameroon). Finally, I collected T. lucayanum specimens on 4 islands of the West Indies.
I obtained geo-coordinates for collection sites from published references, specimen labels, maps, or geography web sites (e.g., earth.google.com, www.geonames.org, www.tageo.com, and www.fallingrain.com). If a site record listed a geographic region rather than a “point locale,” and I had no other record for this region, I used the coordinates of the largest town within the region or, in the case of small islands and natural areas, the center of the region. Published records usually included collection dates. In a number of cases, publications did not include the collection dates for specimens, but I was able to determine the approximate date based on information on the collector's travel dates or limit the date by the collector's date of death. I did not map one record of T. lucayanum apparently found in newly imported goods: specimens from Slough, England collected “on bromeliads ex Brazil” (15.11.1982, L. Kilby, BMNH).
I compiled T. lucayanum specimen records from >75 sites worldwide (Fig. 1). I documented the earliest known T. lucayanum records for 22 geographic areas (countries and West Indies islands; Table 1), including 3 for which I found no previously published records: Gambia, Tortola (British Virgin Islands), and Vieques (Puerto Rico).
I collected T. lucayanum at 7 sites on 4 West Indies islands: Tortola, BVI (2 sites: Great Mountain, by Ridge Road, 18.445°N, 64.626°W, 17 Nov 2005; Martin Spring, 1.3 km up road by ghut, 18.430°N 64.585°W, 17 Nov 2005), Vieques, Puerto Rico (2 sites: Punta Conejo, beach, 18.109°N, 65.376°W, 7 June 2006; Playa Media Luna, sea grape, 18.089°N, 65.448°W, 7 June 2006), New Providence, Bahamas (1 site: Nassau, Ardastra Zoo, 25.073°N, 77.363°W, 5 July 2010), and Jamaica (2 sites: Whitfield Hall, mango, 18.044°N, 76.628°W, 24 Dec 2010; Richmond Vale, forest, 17.969°N, 76.578°W, 24 Dec 2010).
Tetramorium lucayanum has widely scattered records across 12 tropical African countries, presumably the native range of this species, from Sierra Leone in the west to Kenya in the east (Table 1; Fig. 1). The absence of records through central equatorial Africa (e.g., Central African Republic and Uganda) seems likely to be an artifact of the low number of published records of identified ant specimens from this region.
Exotic records of T. lucayanum (Table 1; Fig. 1) come from 7 West Indies islands, 3 sites in Bahia, Brazil, and 3 sites in Europe (the National Botanical Garden and Phoenix Park Zoo in Ireland and in a greenhouse in Italy). All outdoor records of T. lucayanum come from tropical sites, except for 2 subtropical records, both from Nassau, the capital of the Bahamas (25.1°N): the original type locale (Wheeler 1905) and my record from the local zoo, 2.5 km to the west (see results).
Collection records indicate that T. lucayanum inhabits a wide range of habitats in both its native African range and in exotic locales, including forests, beaches, agricultural areas, botanical gardens, urban centers, and temperate greenhouses. In Africa, most records of T. lucayanum come from forest reserves, including Banco Forest Reserve, Ivory Coast (Brown 1964), Pongara National Park, Gabon (Braet & Taylor 2008), Abuko Nature Reserve, Gambia (see Table 1), and Kakamega Forest, Kenya (Hita Garcia et al 2009). Records from urban areas include Kinshasa, Zaire (Forel 1909), Monrovia, Liberia (Brown 1964), Kingston, Jamaica (Brown 1964), and Nassau, Bahamas (see above). Delabie (1994) even recorded T. lucayanum from inside houses in Bahia, Brazil. On Vieques, Puerto Rico, I collected T. lucayanum at 2 beach sites (see results).
Beyond habitat, little is known about the biology of T. lucayanum. Mann (1920) reported that T. lucayanum in Cuba “lives in small colonies under stones.” In Puerto Rico, Smith (1936) reported a colony of T. lucayanum nesting beneath the bark of a tree stump and collected specimens from “a crack in the concrete floor of a barn.” Smith (1936) reported: “it is believed that the workers feed mainly on flesh.” Dejean et al. (1996) found T. lucayanum nesting in 12 termite nests, both occupied and abandoned, in Cameroon forests. Taylor (2010) wrote that T. lucayanum was: “moderately common at the Cocoa Research Institute of Nigeria, Idi Ayunre, probably subarboreal… nests in dead wood on the ground, and in dead wood and crevices on living trees, including cocoa. Will tend aphids. Also found on oil palm.” Future studies of the basic natural history of T. lucayanum (e.g., colony size, food habits) would be valuable.
Several other Tetramorium species from the Old World tropics have become widespread tramp species, including T. bicarinatum, T. caldarium, T. lanuginosum, and T. simillimum (Bolton 1979, 1980; Wetterer 2009b, 2010a). Whereas none of these species have become major pests, all are much more common and widespread than T. lucayanum. Although broadly distributed in Africa and the West Indies, T. lucayanum has been rarely reported. In fact, Torres & Snelling (1997) wrote: “In 18 years of searching for ants in the island of Puerto Rico we have recorded only one apparent extinction, Tetramorium lucayanum.” Most exotic records of T. lucayanum come from Cuba (13 sites) and Jamaica (10 sites), but even on these 2 islands, T. lucayanum appears to be fairly rare. After more than 100 years in the New World, this African ant has persisted and spread, but has shown no discernable ecological impact.
EARLIEST KNOWN RECORDS FOR TETRAMORIUM LUCAYANUM.
I thank M. Wetterer, B. Taylor, and F. Hita Garcia for comments on this manuscript; S. Cover for help, encouragement, and ant identification; F. Hita Garcia, J. Delabie, and A. Dejean for supplying unpublished record information; W O'Brien for GIS help; D. P. Wojcik and S. D. Porter for compiling their valuable FORMIS bibliography; R. Pasos and W. Howerton of the FAU library for processing so many interlibrary loans; Florida Atlantic University and the National Science Foundation (DES-0515648) for financial support.