Tapinoma magnum

Identification
A member of the Tapinoma nigerrimum complex.

Distribution
Seifert et al. (2017) - North Africa from Morocco east to Tunisia, over entire Italy, in Corsica, Sardinia, and southern France.

Distribution based on Regional Taxon Lists
Palaearctic Region: Algeria, Belgium, France, Germany, Greece, Italy, Morocco, Netherlands, Spain, Tunisia.

Biology
Seifert et al. (2017) - The supercolonial Tapinoma magnum has by far the widest distribution among the four species in its group (Tapinoma darioi, Tapinoma ibericum, Tapinoma nigerrimum). It showed the strongest invasive potential of the three supercolonial species and was anthropogenically introduced to nine sites in Germany, Belgium, and the Netherlands (Heller 2011, Dekoninck & al. 2015) which are all situated north of 48° N. Tapinoma magnum became here a pest species with strong local impacts. The beachheads for the German introductions were garden centers and tree nurseries and for the Belgian introduction probably the harbor of Oostende. The frost resistance and low foraging temperatures are remarkable for a Mediterranean ant. Colonies survived in Germany a 14-days frost period with mean air temperatures of -6.6 °C and an absolute minimum of -15 °C without any visible damage (Dekoninck & al. 2015). The German populations of T. magnum showed the last activity in late December at air temperatures of 8 °C and resumed activity after snowmelt in January during a cloudy day and mean and maximum air temperatures of 10.6 and 12.2 °C (Dekoninck & al. 2015; G. Heller, pers. comm.).

In the Mediterranean area, Tapinoma magnum is particularly abundant in open unstable or degraded areas with significant to very strong anthropogenic influence and a weakly developed tree layer. It is more abundant on sandy soils and significantly rarer on rock. If reports from South France (Bernard 1968, 1983) should largely refer to T. magnum, it shows a quite developed tolerance against flooding, occurs in high numbers on irrigated clay soils in areas of market gardening and is found even in swampy habitats. Tapinoma magnum seems to be absent from Iberia except for a beachhead in southernmost Spain. The rarity in Spain is somewhat surprising considering the strong invasive potential of T. magnum. The dominance of the supercolonial Tapinoma ibericum in southern Iberia and of the supercolonial T. darioi in northern Spain probably will have hampered a colonization of these areas by T. magnum. We got the general impression that syntopic occurrence of the three supercolonial species is exceptional.

According to geography of collecting sites (we did not get samples from the authors), the investigations of Blight & al. (2010) can be referred with a fair probability to Tapinoma magnum, but T. darioi cannot be excluded. Blight & al. (2010) showed that their Tapinoma ants limited the spread of the invasive Argentine Ant, Linepithema humile in Corsica and southern France. In space and food competition assays the Tapinoma species of Blight & al. (2010) was more efficient than Linepithema in both interference and exploitative competition, clearly superior in direct fighting, dominated food in 100% of the replicates after one hour, and invaded Linepithema nests while the reverse was never observed. Such isolated laboratory investigations do not necessarily tell us who is the final winner in a particular outdoor confrontation because this is determined not only by basic fighting and recruiting properties but also by ecological adaptation and demographic factors. Strong intraspecific aggressivity between polydomous colonies of T. magnum in gardener's centres of Germany suggests either repeated introductions to the same site or secondary colony splitting – artificially isolated colony fragments developed a significant aggressivity between former nest mates already six months after separation (G. Heller, pers. comm.). Protection of vine and citrus mealybug colonies by T. magnum (a posteriori determined by geographic indication) significantly reduced the effect of several parasitoids and predators with the exception of adult Coccinellidae (Mansour & al. 2012). In south Italy, T. magnum caused direct damage in horseradish cultures by injuring of plants and licking of phloem sap (D. Battaglia, pers comm., sample Potenza-2014.07.15). The nests are subterranean and often very extended, frequently reaching to a depth of 1 m. Nest entrances typically develop to big crater-like domes of ejected soil particles. When occurring in sand dunes (a typical habitat is the back of coastal sand dunes closest to sea) they excavate and maintain long-lasting trails in the sand which are V-shaped in section and up to 5 cm deep. The biggest supercolonies stretch over areas of one hectare or more, should number > 20 million workers and show a permanent exchange of broods between the nests. Single nest spots may contain up to 350 queens. Alates occurred in Italy, Germany, and the Netherlands 10 May ± 26 d [2 April - 17 June] n = 9 (arithmetic mean ± standard deviation [earliest, latest] number of observations). This is apparently the main period but there is an observation of alates in Algeria in August / September. Swarming occurred in May and June, not earlier than 2 - 3 weeks after eclosion from pupae. Most mated gynes stay in or near to the home colony seeking adoption in conspecific nests but their big bodies and well-developed flight muscles should indicate a basically good potency for dispersal flight and independent colony foundation.

Nomenclature

 *  magnum. Tapinoma magnum Mayr, 1861: 41 (q.m.) ITALY.
 * Junior synonym of nigerrimum: Forel, 1876: 61.
 * Status as species: Seifert et al., 2017: 123.

Seifert et al. (2017) - Lectotype male labelled "Savi Pisa.", "v. nigerrim. Magnum det. Mayr" [both labels in Mayr's handwriting], "Lectotype Tapinoma magnum (Mayr, 1861) des. B. Seifert 2012" and "AntWeb CASENT 0915547". One paralectotype gyne on another pin labelled "Savi Pisa.", "v. nigerrim. Magnum det. Mayr" [both labels in Mayr's handwriting] and "Paralectotype Tapinoma magnum (MAYR, 1861) des. B. Seifert 2012". Both specimens stored in NHM Wien.