Numerous ant species have spread around the world through human commerce. For the most part, these “tramp” ants thrive only in disturbed environments and do not penetrate intact natural habitats. But as humans and their disturbance spread, so do tramp ants. The ecological importance of most tramp ants remains undocumented. Several species, however, such as Pheidole megacephala F., are known to have dramatic impacts (Wetterer 2007). For example, Zimmerman (1970) wrote that in Hawaii, “the endemic insect faunas of the lowlands of all the islands mostly have been exterminated throughout the range of the voracious introduced predatory ant Pheidole megacephala.” In Australia, Young (2000) reported: “the rainforest at Howard Springs Nature Park is dominated by the coastal brown ant [P. megacephala], which has eliminated almost all species of native ants, other insect species, snails, spiders and centipedes.”

In addition to P. megacephala, only one other Old World Pheidole species has spread to the New World: Pheidole teneriffana Forel, a species similar in size and general appearance as P. megacephala. Here, I compiled and mapped of P. teneriffana specimen records to evaluate its known worldwide distribution and speculate on its native range and possible impact.

Forel (1893) described P. teneriffana from Tenerife in the Canary Islands, off the northwest coast of Africa. Pheidole teneriffana is the senior synonym of P. teneriffana taina described from Cuba. Taylor (2010) speculated on-line that P. teneriffana is a junior synonym of P. fervens, though this view has not been accepted by other researchers (S. Cover, pers. comm.). Like most Pheidole species, P. teneriffana shows complete dimorphism (i.e., distinct minor and major workers with few, if any, intermediates) with majors having disproportionately large heads compared to minors. It is fairly simple to distinguish P. teneriffana from P. megacephala. In P. teneriffana majors, sculpturing covers the entire dorsal surface of the head, but in P. megacephala, sculpturing is confined to the anterior half of the head, (S. Cover, pers. comm.).

MATERIALS AND METHODS

Using published and unpublished records, I documented the worldwide range of Pheidole teneriffana. I obtained unpublished site records from museum specimens in the collection of the Museum of Comparative Zoology (MCZ) and the Smithsonian Institution (SI). In addition, I used on-line databases with collection information on specimens by Antweb ( www.antweb.org), Asociación Ibérica de Mirmecología ( www.formicidae.org), the Global Biodiversity Information Facility ( www.gbif.org), and Ants of Africa (Taylor 2010). Finally, I collected P. teneriffana specimens on 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.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. I did not map records of P. teneriffana found in newly imported goods or intercepted in transit by quarantine inspectors, e.g., a specimen intercepted in South Africa on goods from Kenya (G. Arnold; SI).

RESULTS

I collected Pheidole teneriffana at 20 sites on 10 West Indian islands: Antigua: St John's, city street (May 2007); Barbados: Bridgetown, city street (Jun 2006) and Oistins Beach (Nov 2003); Barbuda: Codrington, town (Jul 2007); Curaçao: Otrobanda, city street (Aug 2011), Punda, city street (Jul 2004), and Punda, market (Aug 2011); Dominica: Roseau, urban waterfront (Jun 2004); Guadeloupe: Bas du Fort, shopping center (May 2008), Pointe-à-Pitre, by downtown store (Jun 2011), Sainte Anne, town center (May 2008), and Vieux Habitants, town (Jun 2008); Jamaica: Montego Bay, urban produce market (Dec 2010); Martinique: Fort-de-France, urban park (May 2008), Fort-de-France, city street (May 2008), and Robert, urban waterfront (Jul 2011); Montserrat: Old Road Bay, waterfront by an abandoned hotel (Jul 2007); St Lucia: Dennery, waterfront (Jul 2006), Micoud, waterfront (Jul 2006), and Pigeon Island, beach (Nov 2003). In addition, I obtained unpublished records from two other West Indian sites: Dominican Republic: Navarrette at bakery (Dec 2003; S. Cover) and St Lucia: Soufriere (Jan 2005; J. Endeman). I deposited voucher specimens from all sites at the MCZ.

I compiled Pheidole teneriffana specimen records from >200 sites worldwide (Fig. 1). I documented the earliest known P. teneriffana records for 43 geographic areas (countries, island groups, major islands, and US states; Tables 1–3) including 11 West Indian islands for which I found no previously published records: Antigua, Barbados, Barbuda, Curaçao, Dominica, Dominican Republic (Hispañola), Guadeloupe, Jamaica, Martinique, Montserrat, and St Lucia.

Santschi (1919) listed Pheidole teneriffana (identified by G. Arnold), but not P. megacephala, from Samoa. Santschi (1928), however, listed P. megacephala from Samoa, but not P. teneriffana, indicating that he dismissed the earlier identification. Almost half of all mapped site records I found for P. teneriffana came from Egypt (e.g., Santschi 1908, Forel 1913, Alfieri 1931). Although Taylor (2010) regarded the records of P. teneriffana from Egypt to be Pheidole providens, a species otherwise known only from India, I mapped these as P. teneriffana nonetheless.

DISCUSSION

Pheidole teneriffana has widely scattered records from across the greater Mediterranean region (North Africa, Southern Europe, the Middle East, and neighboring islands), though it is unclear which parts of this region, if any, constitute its native range. Santschi (1918) proposed that P. teneriffana probably originated in upper Nile area, in what is now South Sudan, but there are no P. teneriffana specimens known from this region. Wilson (2003) wrote that P. teneriffana “is evidently a native of North Africa and possibly also the Canary Islands.” Emery (1915) and Espadaler & Bernai (2003) considered P. teneriffana as exotic in the Canary Islands. Bytinski-Salz (1953) considered P. teneriffana as a recently arrived exotic in Israel, writing, “Pheidole teneriffana, so far found east only till Egypt, reached Tel Aviv a few years ago.” Collingwood et al. (2004) wrote that P. teneriffana “is probably native throughout northern Africa and appears to be spreading over a wide front in the Middle East, Arabia and the Mediterranean countries.” If P. teneriffana is truly native across North Africa, it is remarkable how few records I found from any North African country other than Egypt: Western Sahara (0 records), Morocco (1 record), Algeria (0 records), Tunisia (2 records), Libya (1 record), and Sudan (1 record).

Fig. 1.

Worldwide distribution records of Pheidole teneriffana. All New World records are previously unpublished, except those from California, Cuba, and Peru.

TABLE 1.

EARLIEST KNOWN RECORDS FOR PHEIDOLE TENERIFFANA FROM THE GREATER MEDITERRANEAN REGION: NORTH AFRICA, THE MIDDLE EAST, SOUTHERN EUROPE, AND NEIGHBORING ISLANDS.

TABLE 2.

EARLIEST KNOWN RECORDS FOR PHEIDOLE TENERIFFANA FROM SUB-SAHARAN AFRICA, EAST ASIA, NORTH EUROPE, AND SOUTH ATLANTIC ISLANDS.

The earliest records of P. teneriffana come from the Canary Islands in the far west of the greater Mediterranean region and from Eritrea in the far southeast, followed by records from Egypt, Tunisia, and Turkey in between (Table 1). This chronology of the earliest known records does not favor any particular hypothesis concerning what part of the greater Mediterranean region may be the original native range of P. teneriffana. Suppositions on where P. teneriffana originated have been based on very little evidence. Genetic analyses may be necessary to evaluate the native range of this species. It seems unlikely that P. teneriffana is native to any of the isolated Old World sites where it has been collected distant from the Mediterranean region, i.e., Ascension, China, England, St Helena, and South Africa.

In the New World, where this species is certainly exotic, I found published P. teneriffana records only from California, Cuba, and Peru (Wilson 2003). The records presented here of P. teneriffana from 11 West Indian islands, all from 2003 or later, suggest that P. teneriffana is actively spreading through this region. In the West Indies, I found P. teneriffana almost exclusively on beaches and at highly disturbed urban sites, particularly in waterfront areas. Santschi (1934), reporting this species from Alexandria, Egypt, similarly noted that P. teneriffana was rarely reported far from seaports. Both in Montego Bay, Jamaica and Pointe-à-Pitre, Guadeloupe, I found P. teneriffana nesting in the cracked concrete at the base of a doorway of a market. In Montego Bay, I found no other ants in the nearby dusty urban street, while in Pointe-à-Pitre, I found P. megacephala nesting at the bases of all the neighboring trees along the sidewalk outside the store. It may be that P. teneriffana is able to nest in microhabitats too dry for other species. Curiously, most Old World records of P. teneriffana are subtropical, but all New World records are tropical, except one from California (Fig. 1), and this one population appears to have been extirpated by another exotic ant, Linepithema humile (Gulmahamad 1999).

TABLE 3.

EARLIEST KNOWN RECORDS FOR PHEIDOLE TENERIFFANA FROM THE NEW WORLD. UNPUBLISHED RECORDS INCLUDE COLLECTOR, MUSEUM SOURCE, AND SITE.

Pheidole teneriffana has remained relatively inconspicuous throughout most of its range, though it may become common in some urban areas. Collingwood et al. (1997) reported that in the United Arab Emirates, P. teneriffana was “very populous in irrigated gardens and along the coast where it appears to be spreading rapidly, and might replace local species.” In the Balearic Islands, Gómez & Espadaler (2006) reported that in Ibiza city, Ibiza, P. teneriffana “has become a common species in the gardens and trees and on sidewalks near the harbour. It seems to be expanding its range in Mallorca from El Arenal gardens where it may become very abundant—to Son Verí to the East and La Lonja (Palma city) in the West, always in disturbed habitats.” Nonetheless, it seems unlikely that P. teneriffana will develop into a major pest species like P. megacephala. Future studies might examine why P. teneriffana and P. megacephala, two species that are morphologically very similar, have such different ecological impacts.