Acromyrmex lundii

Acromyrmex lundii is a host species of the workerless inquiline.

Distribution based on Regional Taxon Lists
Neotropical Region: Argentina, Brazil, Paraguay, Uruguay.

Biology


Römer and Roces (2015) carried out a laboratory study examining this ant's nesting behavior. They noted that it was already known that Acromyrmex lundi leaf-cutting ants:

. . . enlarge existing chambers only if they contain fungus; otherwise they excavate tunnels (Fröhle and Roces 2009). They appear to use their voluminous fungus as a template to adjust the size and shape of the nest chambers (Fröhle and Roces 2009). In addition, it was recently demonstrated that the presence of brood and fungus at a given site triggers the excavation of new nest chambers (Römer and Roces 2014). The brood of A. lundi was shown to be attractive to workers, which aggregate around these items and thereby increase local ant density (Römer and Roces 2014). This locally increased worker density was thought to be responsible for increased excavation activity at the site of brood placement, as compared to alternative sites without brood. The occurrence of brood at a site also led to a change in the shape of the excavated structure, which was round and chamber-like, as compared to a tunnel-like structure excavated at a site without brood (Römer and Roces 2014).

This suggests that the presence of in-nest stores can influence the internal architecture of a nest through a self-organized, likely worker aggregation based adjustment of digging activity. Their study tried to assess how the presence of nest contents (brood and fungus) influenced digging /nest-enlargement behavior in groups of workers placed in a tunnel structure versus a tunnel with a small chamber. They summarized their results as follows: Taken together, our results indicate that the adjustment of both nest size and internal architecture does not simply depend on the number of workers that inhabit a colony. The mechanisms underlying the determination of nest size are flexible and are affected by the available nest space and the presence of in-nest stores. They involve positive and negative feedback loops, such as worker aggregation around stored items and inhibition via the generated space, thus leading to a self-regulated onset and lessening of excavation. The extent of local worker density also influences the internal nest architecture, as ants create cavities when excavating in a concentrated manner, and tunnels when they are more dispersed. Another important mechanism by which ants dynamically adjust the size of their nests is the opportunistic deposition of excavated soil pellets at unused spaces, effectively downsizing their nest.

Barrera et al. (2015) studied the diversity of leaf cutting ants along a forest-edge-agriculture habitat gradient. Their study site, in Chaco Serrano of Central Argentina, had forest remnants of various sizes within an agriculture area with wheat, soy and maize. A. lundii was the moderately abundant (21% of the 162 Acromyrmex colonies sampled). This species was found in the forest interior but was much less abundant there than Acromyrmex crassispinus. Along the forest edge it was similar in abundance to Acromyrmex striatus, with A. crassispinus also present but occurring at a slightly lower abundance. A few colonies of Acromyrmex heyeri and Acromyrmex silvestrii were also found along the forest edge. Ten Acromyrmex nets were found within 5m of the forest edge but none were sampled 25m from the forest edge in the croplands.

The ascomycetous yeast species Wickerhamomyces spegazzinii has been isolated from the fungus garden of this species (Masiulionis & Pagnocca, 2016).

Nomenclature

 *  lundii. Myrmica lundii Guérin-Méneville, 1838: 206 (q.m.) BRAZIL. Roger, 1863a: 201 (w.); Forel, 1885a: 356 (w.); Wheeler, G.C. 1949: 675 (l.). Combination in Atta: Roger, 1863a: 200; in Atta (Acromyrmex): Forel, 1885a: 356; in Acromyrmex: Forel, 1913l: 237. Senior synonym of bonariensis: Gallardo, 1916d: 331; of risii: Santschi, 1925a: 384; of dubia: Gonçalves, 1961: 150. See also: Bruch, 1921: 192. Current subspecies: nominal plus boliviensis, carli, decolor, parallelus.
 * bonariensis. Atta (Acromyrmex) pubescens var. bonariensis Emery, 1905c: 52 (w.) ARGENTINA. Combination in Acromyrmex: Bruch, 1914: 216. Subspecies of lundii: Bruch, 1914: 216; Santschi, 1925a: 385. Junior synonym of lundii: Gallardo, 1916d: 331; Gonçalves, 1961: 150.
 * dubia. Atta (Acromyrmex) laticeps var. dubia Forel, 1908c: 350 (w.) BRAZIL. Combination in Acromyrmex: Emery, 1924d: 349. Subspecies of lundii: Santschi, 1925a: 385. Junior synonym of lundii: Gonçalves, 1961: 150.
 * risii. Atta (Acromyrmex) lundii var. risii Forel, 1908c: 350. (w.) ARGENTINA. Combination in Acromyrmex: Forel, 1913l: 237. Junior synonym of lundii: Santschi, 1925a: 384.