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Species
Linepithema humile (Mayr, 1868)
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Native to the Parana river drainage of South America, the small, brown Argentine ant Linepithema humile has spread to become a highly destructive invasive species around the world, forming super colonies especially in warm climates, island environments (for example, New Zealand) and areas where humans have caused environmental disturbances. These small (workers are 2-3 mm long) ants are easily spread accidentally in human transport of goods, and are successful due to their generalist and omnivorous habits. Argentine ant workers forage on nectar, as well as other insects, and effectively displace native species of ants. A significant part of the Argentine ant diet comes from the hemipteran, mealybugs, scale and aphid honeydew and the ants readily protect these insects to take advantage of this food source. Because of this mutalistic relationship, the Argentine ant has indirectly become a threat to crops, which are damaged by boosted pest populations. Although Argentine ants do not bite or sting or directly threaten humans, this highly mobile, gregarious and difficult to control species is tolerant of diverse conditions and food, posing a severe threat to the ecosystems and biodiversity of the countries it invades, and is considered among the worst 100 of the world’s invasive species.
(CABI 2011; Daugherty and Hung; Lowe, Browne and Boudjelas 2000; Wikipedia 2011)
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Rights holder/Author | Dana Campbell, Dana Campbell |
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Diagnosis of worker among Antkey species. Antenna 12-segmented. Antennal scape length less than 1.5x head length. Eyes medium to large (greater than 6 facets); do not break outline of head; placed distinctly below midline of face. Antennal sockets and posterior clypeal margin separated by a distance less than the minimum width of antennal scape. Anterior clypeal margin variously produced, but never with one median and two lateral rounded projections. Mandible lacking distinct basal angle. Profile of mesosomal dorsum with two distinct convexities. Dorsum of mesosoma lacking a deep and broad concavity; lacking erect hairs. Promesonotum separated from propodeum by metanotal groove. Propodeum with dorsal surface not distinctly shorter than posterior face; angular, with flat to weakly convex dorsal and posterior faces. Propodeum and petiolar node both lacking a pair of short teeth. Mesopleura and metapleural bulla covered with dense pubescence. Propodeal spiracle bordering posterior margin of propodeal profile. Waist 1-segmented. Petiole upright and not appearing flattened. Gaster armed with ventral slit. Erect hairs lacking from cephalic dorsum (above eye level), pronotum, and gastral tergites 1 and 2. Dull, not shining, and color uniformly light to dark brown. Measurements: head length (HL) 0.56–0.93 mm, head width (HW) 0.53–0.71 mm.
Among the species treated here, Linepithema humile is most easily confused with the Argentine Ant, L. iniquum. It can be separated from that species by the following characters: (1) the mesopleura and metapleural bulla are covered in pubescence and have a dull (versus glabrous) surface; (2) erect hairs are lacking (versus present) on cephalic dorsum (above eye level), gastral tergites 1 and 2, and often present on pronotum; (3) the profile of mesosomal dorsum has two (versus three) distinct convexities; (4) the propodeum is angular (versus globular) and is flat or weakly convex with dorsal and posterior faces (versus strongly and uniformly convex); and (5) the propodeal spiracle is bordering (versus distinctly anterior to) the posterior margin of propodeal profile.
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Rights holder/Author | Eli Sarnat, Antkey |
Source | http://antkey.org/node/32627 |
Barcode of Life Data Systems (BOLDS) Stats
Public Records: 34
Specimens with Barcodes: 80
Species With Barcodes: 1
Records
(Map 46): Sofia Basin: Sofia; Northern Black Sea coast: Varna; Southern Black Sea coast: Burgas [ Atanassov and Dlusskij 1992 (all as Iridomyrmex humilis )].
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Source | http://dx.doi.org/10.3897/zookeys.62.430 |
United States
Rounded National Status Rank: NNA - Not Applicable
License | http://creativecommons.org/licenses/by-nc/3.0/ |
Rights holder/Author | NatureServe |
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(Worker, Figs. 1 and 5; queen, Figs. 8, 9, and 10; male, Figs. 11, 12, and 13)
Hypoclinea humilis Mayr 1868: 164. Worker description.
Iridomyrmex humilis (Mayr); Emery 1888: 386-388. First combination in Iridomyrmex .
Iridomyrmex humilis (Mayr); Wheeler 1913: 27-29. Male and queen description, worker redescription.
Iridomyrmex humilis (Mayr); Newell and Barber 1913: 38-39 (egg), 40-41 (larva), 42-45 (worker, male, queen pupae).
Iridomyrmex humilis variety arrogans Chopard 1921: 241-245. Syn. Nov. Junior synonym of I. humilis by Bernard 1967: 251. Restored to subspecies of L. humile by Shattuck 1992: 16.
Iridomyrmex riograndensis Borgmeier 1928: 64. Syn. Nov.
Iridomyrmex humilis (Mayr); Wheeler and Wheeler 1951: 186-189. Summary of larval biology.
Linepithema riograndense (Borgmeier) ; Shattuck 1992: 16.
Linepithema humile (Mayr); Shattuck 1992: 16. First combination in Linepithema .
Type Material Examined
Additional Material Examined
South American material examined given in Table 1. Specimens collected outside of South America are listed below. Given the large quantity of Argentine ants collected in California, I only list here a representative subsample of California specimens that were given a relatively thorough examination under the microscope (e.g., setal counts and measurements).
AUSTRALIA. Sydney [MZSP];Victoria (s. loc.) [BMNH].BELGIUM. Bruxelles Capitale: Brussels [BMNH, NHMB],Brussels Botanical Garden [MHNG].BERMUDA. Bermuda (s. loc.) [BMNH].CAMEROON. Centre-Sud: Nkoemvom [bMNh].FRANCE. Provence-Alpes-Co te d'Azur: Cannes [MCZC, NHMB],Castellane [BMNH],Hyeres [BMNH],Ste. Maxime [NHMB];Midi-Pyrenees: Toulouse [IFML].GERMANY. Berlin: Botanical Garden[MHNG].ITALY. Campania: nr. Naples [BMNH];Liguria: San Remo [NHMB];Sicilia: Palermo[BMNH];Toscana: Monte Argentario Giannella [BMNH],Orbetello [BMNH];Varazze (Savona) [MZSP].LESOTHO. Maseru: Maseru [BMNH]. MO- ROCCO. Tanger, Tangier [USNM].MEXICO. Baja California: Ensenada,Cortera FR [AVSC];Baja California Sur: Guerrero Negro [AVSC];Distrito Federal: Mexico City [BMNH],Distrito Federal (s.loc.) [WPMC].NAMIBIA. Erongo: Swakopmund [BMNH].POLAND. Dolnoslaskie: Breslau [NMHB].PORTUGAL. Faro: Algarve,Luz nr. Lagos [bMNh];Lisboa: Cascais [USNM],Estoril [USNM],Lisbona [MCZC, NHMB],Mafra [USNM],Praia das Macas [USNM];Madeira: Funchal [MCZC, NHMB],Porto Moniz [BMNH],RibeiraBrava [BMNH],Ilheu Chao [BMNH],Porto Santo [BMNH],Sao Vicente [BMNH],Vale de Paraiso [BMNH],Praia Formosa [BMNH],Porto da Cruz [BMNH],Feiteiras [BMNH],Caramujo [BMNH],Lower Levada [BMNH],Madeira Is. (s. loc.) [BMNH, MHNG, NHMB];Porto: Leca [BMNH],Oporto [BMNH].SOUTH AFRICA.Eastern Cape: Queenstown [BMNH],Somerset East [BMNH];Mpumalanga: Nelspruit[BMNH];Northern Cape: Colesberg [ALWC];Western Cape: Capetown [BMNH],Table Mt. [BMNH],nr. George [BMNH].SPAIN. Andalucia: Malaga [USNM];Canarias: Arenara [BMNH],Cruz de Tejeda [BMNH],Gran Canaria, Las Palmas, Telde [BMNH, MCZC, USNM],Orotava [BMNH],Santa Brigida [BMNH],Tenerife, Agua Mansa [NHMB],Tenerife, Ladera de Guimar [BMNH],Tenerife, Volcan de Guimar [NHMB],Tenerife (s. loc.) [BMNH];Cataluna: Playa de Aro [NHMB];Galicia: Mte. Ferro b. Bayona [BMNH];IslasBaleares: Minorca, CalaForcat[BMNH].UNITED KINGDOM. Edinburgh: Edinburgh[BMNH];Sussex: Lewes [BMNH];Eastborne[BMNH];Exeter [BMNH];Windsor [BMNH];Glasgow [BMNH];W. Maidstone, Kent [bMNh];Chillingham [BMNH];Farnham House Lab, Imperial Bureau of Entomology [BMNH].UNITED STATES. Alabama: Lowdnes Co., Ft. Deposit [USNM];California: Alameda Co., Berkeley [UCDC, USNM];Humboldt Co., Redway [ALWC];Los Angeles Co., Pasadena[MZSP, USNM], Monterrey Co., Big Sur [ALWC];Orange Co., Bolsa Chica Marsh [MZSP];Riverside Co., Lake Skinner Camp [AVSC];Sacramento Co., Sacramento [UCDC];San Diego Co., UC Elliot Reserve [AVSC];San Diego Co., San Diego [UCDC];San Diego Co., E. San Diego [UCDC];San Diego Co., Pacific Beach [UCDC];San Diego Co., Mission Hills [UCDC];San Diego Co., Kate Sessions Park [UCDC];San Diego Co., Balboa Park [UCDC];San Diego Co., Point Loma [UCDC];San Joachin Co., Caswell State Park [PSWC];San Luis Obispo Co., Oso Flaco Lake [LACM];San Mateo Co., Colma [USNM];San Mateo Co., San Bruno Mt. [PSWC];Santa Clara Co., South Coyote [PSWC];Sonoma Co., Russian R. 6k E. Healdsburg [UCDC];Yolo Co., 6kW Capay [PSWC];Yolo Co., Davis [PSWC, UCDC];Yolo Co., Grasslands Regional Park, 8k SW Davis [PSWC, UCDC];Florida: Escambia Co., Gonzalez [MCZC];Louisiana: Plaquemines Co., Happy Jack [BMNH], Orleans Co., New Orleans [BMNH], Lousiana (s. loc.) [BMNH];Mississippi: Coahoma Co., Clarkesdale [USNM], Copiah Co., Hazelhurst [MCZC], Oktibbeha Co., Starkville [BMNH];South Carolina: York Co., York [BMNH].
. 1-7. Linepithema workers. 1. L. humile , lateral view. Specimen from Neembucu, Paraguay. 2. Undescribed Linepithema species, mesosoma, lateral view. Specimen from Parque Nacional El Palmar, Entre Rios, Argentina. 3. L. iniquum , mesosoma, lateral view. Specimen from the Reserva Natural del Bosque Mbaracayua, Paraguay. 4. Undescribed Linepithema species, mesosoma, lateral view. Specimen from the Reserva Natural del Bosque Mbaracayu, Canindeyu, Paraguay. 5. L. humile , head, full face view, same specimen as 1. 6. L. oblongum , head, full face view. Specimen from Infiernillos, Tucumaan, Argentina. 7. Undescribed Linepithema species, head, full face view. Same specimen as in Fig. 2.
Worker Measurements. HOLOTYPE: HL 0.74, HW 0.66, MFC 0.16, SL 0.76, FL 0.65, LHT 0.68, PW 0.45, ES 2.93, SI 115, CI 89.
Others (n = 81): HL 0.62-0.78, HW 0.53-0.72, MFC 0.14-0.18, SL 0.62-0.80, FL 0.52-0.68, LHT 0.57-0.76, PW 0.35-0.47, ES 1.98-3.82, SI 108-126, CI 84-93.
Worker Diagnosis. A large (HL> 0.62 mm) slender Linepithema . Head in full-face view longer than broad (CI 84-93), narrowed anteriorly and reaching its widest point just posterior to the compound eyes. Lateral margins broadly convex, grading smoothly into posterior margin. Posterior margin of head straight in smaller workers to weakly concave in larger workers. Compound eyes large (ES 1.98-3.82), comprising 82- 110 ommatidia (normally around 100). Antennal scapes long (SI 108-126), as long or slightly longer than HL and easily surpassing posterior margin of the head in full-face view. Maxillary palpi relatively short, segments 4 and 5 both noticeably shorter than segment2.
Pronotum and mesonotum forming a continuous convexity in lateral view, mesonotal dorsum nearly straight, not angular or strongly impressed, although sometimes with a slight impression in the anterior half.
Metanotal groove moderately impressed. Propodeum in lateral view inclined anteriad. In lateral view, dorsal propodeal face meeting declivity in a distinct though obtuse angle, from which the declivity descends in a straight line to the level of the propodeal spiracle.
Dorsum of head, mesosoma, petiole, and abdominal tergites 3 and 4 (= gastric tergites 1 and 2) devoid of erect setae (very rarely with a pair of small setae on abdominal tergite 4). Clypeus bearing a pair of long, forward-projecting setae. Abdominal tergites 5 and 6 each bearing a pair of long, erect setae. Ventrum of metasoma with scattered erect setae. Gula with a pair of short setae. Body and appendages, including gula, the entire mesopleuron, and abdominal tergites, covered in dense pubescence.
Country Admin. Argentina Buenos AiresLocality BocaStatusLatitude Longitude 34° 38' S58° 21'Collection ALWCArgentina Buenos AiresBuenos Aires34° 36' S58° 28' WBMNH, MHNG, NHMB, NHMW, UCDCArgentina Buenos AiresCampana34° 12' S58° 56' WALWCArgentina Buenos AiresReserva Costanera Sur34° 07' S58° 21' WAVSCArgentina Buenos AiresIsla Martin Garcia34° 21' S58° 16' WMACN, NHMBArgentina Buenos AiresLa Plata34° 56' S57° 57' WNHMBArgentina Buenos AiresLima-Zarete34° 03' S59° 12' WIFMLArgentina Buenos AiresOlivos34° 31' S58° 30' WMACNArgentina Buenos AiresReserva Otamendi34° 14' S58° 54' WALWC, AVSC, IFMLArgentina Buenos AiresRosas- F.C.Sud35° 58' S58° 56' WMACNArgentina Buenos AiresSanta Coloma34° 26' S59° 02' WALWCArgentina ChubutRawson43° 18' S65° 06' WPSWCArgentina CorrientesAyo. Cuay Grande28° 47' S56° 17' WALWCArgentina CorrientesCorrientes27° 28' S58° 50' WMACNArgentina CorrientesIta Ibate27° 25' S57° 10' WAVSCArgentina CorrientesPort Alvear29° 07' S56° 33' WAVSCArgentina CorrientesSto. Tome28° 33' S56° 03' WIFMLArgentina Entre Rios10k S Medanos33° 29' S58° 52' WALWCArgentina Entre RiosColon32° 15' S58° 07' WAVSCArgentina Entre RiosDiamante32° 01' S60° 39' WALWCArgentina Entre RiosEst. Sosa31° 44' S59° 55' WMACN, MHNG, NHMBArgentina Entre RiosParque Nacional El Palmar31° 53' S58° 13' WAVSCArgentina Entre RiosParque Nacional Pre Delta32° 7' S60° 38' WAVSCArgentina Entre RiosPort Ibicuy33° 48' S59° 10' WAVSCArgentina Entre RiosVictoria32° 38' S60° 10' WALWCArgentina Entre RiosVillaguay31° 51' S59° 01' WNHMBArgentina FormosaClorinda25° 17' S57° 43' WIFMLArgentina FormosaFormosa26° 11' S58° 11' WMACN, NHMBArgentina FormosaMojon de Fierro26° 03' S58° 03' WIFMLArgentina La RiojaAmingai28° 50' S66° 54' WALWC, IFMLArgentina La RiojaChuquis28° 54' S66° 58' WALWCArgentina MisionesParque Nacional Iguazui25° 42' S54° 26' WIFMLArgentina MisionesPosadas27° 23' S55° 53' WMZSPArgentina Santa Fe10k E Santa Fe, Ruta 16831° 41' S60° 34' WALWCArgentina Santa FeFives Lille30° 09' S60° 21' WNHMBArgentina Santa FePort Ocampo28° 30' S59° 16' WAVSCArgentina Santa FeRosario32° 57' S60° 40' WMACNArgentina Tucumai nTichuco26° 31' S65° 15' WALWCBrazil AmazonasManaus03° 07' S60° 02' WMZSPBrazil GoiasAnapolis16° 20' S48° 58' WMZSPBrazil Mato Grosso do Sul Corumba Faz. Sta. Blanca19° 01' S57° 39' WMZSPBrazil Mato Grosso do Sul Corumba Pto. Esperanga19° 37' S57° 27' WMZSPBrazil Mato Grosso do Sul Passo do Lontra19° 34' S57° 01' WPSWC, UCDCBrazil Mato Grosso do Sul Pto. Murtinho21° 42' S57° 52' WMZSPBrazil Rio de JaneiroRio de Janeiro22° 54' S43° 14' WMCSN, MCZC, MHNGBrazil Rio Grande do SulN. Wurtemberg28° 18' S53° 30' WMZSPBrazil Rio Grande do SulPelotas31° 46' S52° 20' WBMNHChile La AraucaniaTemuco38° 44' S72° 36' WMZSPChile SantiagoSantiago, Metropolitan area33° 27' S70° 40' WAVSCChile Valparaiso10k E Vina del Mar33° 00' S71° 31' WAVSCColombia QuindioArmenia4° 30' S75° 42' WWPMCEcuador PichinchaCarapungo0° 05' S78° 30' WALWCEcuador PichinchaMitad del Mundo0° 00' S78° 27' WALWCEcuador PichinchaQuito0° 11' S78° 30' WQCAZParaguay Alto ParaguayPto. 14 de Mayo20° 23' S58° 08' WMCSNParaguay Asuncioi nAsuncion25° 16' S57° 40' WIFML, MACN, NHMB, USNMParaguay BoqueronP.N. Defensores del Chaco, Cerro Leon20° 25' S60° 20' WALWCParaguay CentralSan Lorenzo25° 20' S57° 31' WALWCParaguay CordilleraSan Bernadino25° 16' S57° 19' WMHNGParaguay N eembucuPilar26° 52' S58° 18' WALWCParaguay Neembucu26° 52' S57° 47' WALWCParaguay Pte. HayesBenjamin Aceval24° 58' S57° 34' WUSNMParaguay Pte. HayesRio Confuso, Ruta Trans-Chaco25° 06' S57° 33' WALWC, IBNPParaguay Pte. HayesVilla Hayes25° 06' S57° 34' WALWC, IBNPParaguay Pte. Hayes5k SE Pozo Colorado23° 33' S58° 46' WALWCParaguay Pte. HayesRt. 5 3k SE Concepcion23° 27' S57° 27' WALWCParaguay San PedroPto. Rosario24° 30' S57° 00' WALWCPeru LimaLos Condores12° 03' S77° 03' WMZSPUruguay ColoniaCarmelo33° 59' S58° 17' WMACN, NHMBUruguay ColoniaColonia de Sacramento34° 28' S57° 51' WAVSCUruguay MontevideoMontevideo34° 51' S56° 10' WMACN, NHMB, NHMW
Body and appendages concolorous, most commonly a medium reddish or yellowish brown but ranging in some populations from testaceous to dark brown, never yellow or piceous. Integument shagreened and lightly shining.
Worker Geographic Variation. Specimens from introduced populations outside of South America tend to fall toward the upper range of size variation in nearly all measurements, although there is considerable variation both in the native and the introduced ranges. The holotype worker from Buenos Aires is among the largest ants from either range. Some Paraguayan populations, particularly those farther than 10 km from the Paraguay River, have a slightly smaller eye size (<95 ommatidia) and tend to be smaller than ants in the southern Parana drainage and along the major riverways. In general, Paraguayan specimens vary more in color than specimens from elsewhere, from testaceous to dark brown. The diagnostically sparse pilosity is generally consistent across all specimens, but several workers from Campana, Buenos Aires, have small erect setae on abdominal tergite 4 (= gastric tergite 2). These Campana workers otherwise fall within the range ofvariation for L. humile , and males from the same series clearly belong to L. humile .
Queen Measurements. (n = 13) HL 0.83-0.92, HW 0.83-0.93, SL 0.81-0.89, WGL 4.42-4.51, WL 1.67- 2.09, FL 0.78-0.90, LHT 0.88-0.97, ES 7.3-9.4, SI 96- 102, CI 93-101.
Queen Diagnosis. A robust species, dificult to distinguish from queens ofrelated Linepithema , with long antennal scapes and large eyes. Head in full face view normally somewhat longer than broad (CI 93-101), lateral margins convex and broadly curved into the posterior margin. Posterior margin ofhead straight to slightly concave, never deeply or conspicuously concave. Eyes large (ES 7.3-9.4). Antennal scapes long (SI 96 -102) and nearly equal to head length.
Entire body covered in a dense pubescence, a bit thicker and longer than that of the worker. Pilosity is also more developed than in the worker, with 2-11 (mean = 6) erect setae on the mesoscutum, 1-7 (mean = 4) erect setae on the scutellum, and 1-10 (mean = 3) erect setae on abdominal tergite 3, including the posterior row. Color as for the worker.
Queen Geographic Variation. Alate queens are much more common in collections from the native range than in collections from outside of South America. This observation is unlikely to be a sampling artifact given how heavily the introduced populations are represented in collections.
Male Measurements. (n = 25) HL 0.56-0.71, HW 0.56-0.74, SL 0.13-0.16, MML 1.40-1.96, MMW 0.76- 1.12, WGL 2.55-3.26, FL 0.60-0.77, LHT 0.51-0.66, SI 12.8-15.4, CI 98.2-106.0.
Male Diagnosis. A robust ant, larger than the worker, with an exceptionally well-developed mesosoma. Head about as broad as long in full face view (CI 98.2-106.0) and somewhat dorso-ventrally compressed in lateral view. Eyes large, occupying much of antero-lateral surface of head and forming the anterior margin ofthe head lateral to the clypeus and the lateral margin of the head anterior to midpoint. Ocelli large and in full frontal view set above the adjoining postero-lateral margins. Anterior clypeal margin straight to broadly convex. Mandibles small, having a single apical tooth and four to eight denticles along the masticatory margin and rounding into the inner margin. Masticatory margin relatively short, about the same length as the inner margin. Inner margin roughly parallel to, or even converging distally with, the exterior lateral margin.
Mesosoma well-developed, considerably wider than head width, and larger in bulk and in length than metasoma. Mesoscutum greatly enlarged, projecting forward in a convexity overhanging the pronotum. Scutellum large, convex, nearly as tall as mesoscutum and projecting well above the level ofthe propodeum. Propodeum overhanging petiolar node, and declivitous face strongly concave.
Wings short relative to mesosomal length (Fig. 17) and bearing a single submarginal cell. Wing color whitish or yellowish, with dark brown veins and stigma. Petiolar scale with a broad crest and taller than the length of the node. Ventral process well developed. Gaster oval in dorsal view, nearly twice as long as broad. Parameres terminating as rounded pilose lobes. Digitus short, with a sharp, downturned terminal ilament.
Dorsal surfaces of body largely devoid of erect setae, occasionally with a few ine, short setae scattered on mesoscutum, scutellum, and posterior abdominal tergites. Venter of gaster with scattered setae. Pubescence dense on body and appendages, becoming sparse only on the medial propodeal dorsum. Color as for the worker.
Male Geographic Variation. As in workers, specimens from introduced populations outside of South America tend to fall in the upper range of size variation.
Discussion
Taxonomy. These taxonomic results support current nomenclatural use. The holotype worker of Mayr's Hypoclinea humilis falls neatly within the range of variation present in the Argentine ant both in South America and in locations around the world where the ant is invasive (Figs. 15 and 16). The only older species-level name in the genus, Linepithema fuscum Mayr 1866, pertains to a male ant whose slender build, elongate genitalia, and distinct queen-like wing venation indicate only a distant relation to L. humile . Borgmeier's species riograndense , described from Rio Grande do Sul, Brazil, is clearly conspecific with L. humile and is synonymized here. Borgmeier's specimen identifications in MZSP reveal that he considered the name humile to apply to a common, probably undescribed southern Brazilian Linepithema with short antennal scapes and more extensive pilosity. The aptly named subspecies L. humile arrogans Chopard , described from introduced L. humile populations in southern France, was probably inadvertently resurrected by Shattuck (1992) from an earlier synonymy. Here, I return arrogans to synonymy because there is no reason to view introduced Argentine ant populations as being heterospeciic.
Diagnosis . L. humile diagnosis is straightforward in the male caste. The distinctive bulky males of humile are not easily confused with males of any other species. Males of closely related forms share structural similarities with L. humile (e.g., the undescribed species in Fig. 14) but are considerably smaller (Fig. 17) with a much less developed mesosoma. The lack of known intergrades strongly supports the speciic status of L. humile . The only other congeneric males that share the size of humile are montane Andean and Caribbean forms associated with L. fuscum , but these are unlikely to be confused with L. humile . Linepithema fuscum -group males are structurally divergent (Shattuck 1992), with an unusually elongate habitus, a propodeum with a convex posterior face in lateral view, two submarginal cells in the forewing, and considerably longer wings relative to maximum mesosomal length (Fig. 17).
Diagnosis is somewhat more problematic in workers, as no single character serves to separate L. humile from congeneric species. Table 2 provides a summary of the minimum combination of three character states that can diagnose nearly all L. humile worker specimens over the full geographic distribution of Linepithema . Figure 15 shows a consistent though not absolutely diagnostic difference in eye size versus head length between the large-eyed L. humile and all other non-humile specimens. Figure 16 plots antennal scape length versus head length in L. humile versus several other species, excluding the distinct long-scaped species L. oblongum , L. leucomelas , and ants of the L. iniquum -complex. These species are readily recognizable with other characters. Specifically, iniquum-complex ants have a strongly impressed mesonotal dorsum (Fig. 3), pronotal setae, and smaller eyes (ES <2.0). L. leucomelas has a distinct white/brown bicoloration reminiscent of the ant Tapinoma melanocephalum (F.) 1793, standing setae on gastric tergites 1 and 2, and smaller eyes (ES <2.0).
L. oblongum (Fig. 6) is the species most similar to L. humile . This poorly known ant seems to be conined to the high Andes in northern Argentina and Bolivia. Workers share the sparse pilosity and a similar mesosomal proile with L. humile , but they are somewhat more elongate (CI 81-88, mean = 84 in L. oblongum ; CI 84 -93, mean = 90 in L. humile ) and have relatively smaller eyes (Fig. 18). Linepithema oblongum workers also have a noticeably smoother and shinier integument on the gastric dorsum than L. humile , and most workers have only sparse pubescence on gastric tergites2 and 3, although some of the larger specimens within a series may retain a dense pubescence. Males of L. oblongum are much smaller than those of L. humile (MML <1.1), and they lack the extraordinary mesosomal development of L. humile males. This species may be the sister taxon of the Argentine ant, a possibility that is currently being pursued with molecular genetic data (unpublished data).
. The Argentine ant's native distribution seems to be limited to the Parana River drainage (Fig. 19), conirming the conclusion of Tsutsui et al. (2001). South American records of L. humile outside the Paranaa drainage are invariably from urban areas, an observation that strongly supports the notion of recent introduction by human commerce. Paranaa drainage records are also more abundant than nonParanaa records (49 versus 8). Furthermore, most records fall within a few kilometers of the largest rivers: the Parana, the Paraguay, and the Uruguay. This is unlikely to be a sampling artifact, as evidenced from numerous records of other, non-humile species distant from major rivers (Fig. 20).
Records of L. humile in South America show the following pattern: patchy local abundance in low areas of the Parana River drainage; common along major rivers (perhaps aided through frequent natural dispersal along the river); and very recent dispersal out of the Parana drainage with human activity. Interestingly, some of the more morphologically divergent L. humile , including those with color variations and smaller compound eyes, are found>10 kilometers away from large rivers in the northern part of the native range. It is unlikely that this variation reflects the existence ofcryptic species, given that much ofthe variation is allopatric and that L. humile males show remarkable consistency in diagnostic traits across populations. Specimens from the southern native range tend to look more like the common pest L. humile , although there is still a fair amount of variation. Overall this pattern raises the hypothesis of a northern origin for the species with later dispersal along the rivers. This hypothesis could be tested with genetic data in a phylogeographic framework (Avise 2000).
The history and biology of the Argentine ant in its native range is liable to be complex. Argentine ants likely move along river channels during periods of natural disturbance, and some of the native range records probably correspond to recent local introductions through human commerce. It bears noting that L. humile is present in many urban areas along the Paranaa and Paraguay rivers. The preponderance of Argentine ant records from lat, expansive lood plains suggests that records from fast-running, deeply channelized stretches of the Upper Parana such as Argentina's Foz do Iguacu also may not represent native populations.
The morphological diversity in native-range L. humile raises the issue of intraspeciic diversity in other aspects of Argentine ant biology. Tsutsui and Case (2001) note variation in colony structure in the native range, and there also may be variation in mating systems and in colony life history. Studies that make use of contrasts between Argentine ant biology between native and introduced ranges would do well not to treat native range L. humile as a monolithic entity.
Rather, care should be taken to chose L. humile populations that are most likely to be close relatives of the introduced populations under study. Genetic work of Tsutsui et al. (2001) indicates that a southern Parana population represents the source population for California L. humile . It also remains a possibility that some biological changes that contribute to the Argentine ants' invasive success occurred within the native range before introduction. Detailed studies ofArgentine ant biology mapped onto a population-level phylogeny over the whole of the native range could determine if this were the case, as well as shed light on the sequence of evolutionary events leading to invasiveness in Argentine ants.
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Rights holder/Author | No known copyright restrictions |
Source | http://antbase.org/ants/publications/20351/20351.pdf |
Rounded Global Status Rank: GNR - Not Yet Ranked
License | http://creativecommons.org/licenses/by-nc/3.0/ |
Rights holder/Author | NatureServe |
Source | http://explorer.natureserve.org/servlet/NatureServe?searchName=Linepithema+humile |
The Argentine ant, Linepithema humile, is among the world’s most notorious, successful and well-studied invasive ant species. Linepithema humile is a nondescript, soft-bodied, small (2.2–2.6 mm), dull light to dark brown ant with large inset eyes. The species is native to the Paraná River drainage in South America, which stretches across northern Argentina, Uruguay, Paraguay, and southern Brazil (Wild, 2004). Linepithema humile thrives in Mediterranean climates, and over the past century it has spread to across the globe by human-mediated transport to Chile, western and southern North America, Hawaii, New Zealand, Easter Island, Australia, Japan, Africa, and southern Europe (Suarez et al., 2001; Wetterer et al., 2009). Argentine ants are significant pests, and are documented to cause substantial harm to native arthropod communities (Cole et al., 1992; Rowles & O'Dowd, 2009a), vertebrate communities (Suarez & Case, 2002; Suarez et al., 2005), plant communities (Christian, 2001; Ives et al., 2011; Lach, 2005; Rowles & O'Dowd, 2009b). Argentine ants are also significant agricultural pests (Vega & Rust, 2001)and urban/residential pests (Klotz et al., 2008a; Klotz et al., 2008b).
License | http://creativecommons.org/licenses/by-sa/3.0/ |
Rights holder/Author | Eli Sarnat, Antkey |
Source | http://antkey.org/node/32627 |
I [introduced species]
License | |
Rights holder/Author | No known copyright restrictions |
Source | http://antbase.org/ants/publications/21008/21008.pdf |
Comercial
L. humile no tiene un valor comercial, no posee ningún interés económico en particular (Krushelnycky &Joe, 1997).
License | http://creativecommons.org/licenses/by-nc-sa/2.5/ |
Rights holder/Author | CONABIO |
Source | No source database. |