Amoimyrmex striatus

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. striatus was the moderately abundant (17% of the 162 Acromyrmex colonies sampled). Along the forest edge it was similar in abundance to Acromyrmex lundii, with Acromyrmex crassispinus also present but occurring at a slightly lower abundance. A few colonies of Acromyrmex heyeri and Amoimyrmex 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. A. striatus was not found in the forest interior but was the most common species in the cropland matrix close to the forest edge. This suggests this species may do well in disturbed areas. In some regions A. striatus is known as a pest species (Diehl-Fleig, 1993).

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

Biology
Jofre et al. (2018) - Amoimyrmex striatus is one of the most common leaf-cutting ant species in Argentina (Farji-Brener & Ruggiero, 1994). This species constructs relative small subterranean nests in areas of low vegetation cover. Workers forage at close distances from the nest without a defined network trail system (Boneto, 1959; Diehl-Fleig, 1995). Amoimyrmex striatus consumes a high percentage of species available in the environment (Armani & Quirán, 2007; Nobua-Behrmann, 2014), and their degree of selectivity or opportunism depends on the availability of resources within the proximity of their colonies (Farji-Brener & Protomastro, 1992; Pilati et al., 1997; Franzel & Farji-Brener, 2000; Armani & Quirán, 2007; Nobua-Behrmann, 2014).

Foraging
Nobua-Behrmann et al. (2017) studied temporal and thermal aspects of Amoimyrmex striatus foraging behavior in the Monte Desert in Argentina where this species co-occurs with Acromyrmex lobicornis. Amoimyrmex striatus colonies were active during spring and summer, with no signs of foraging activity during winter. Foraging intensity was highest during spring and summer, with up to 90 ants (foragers returning to the nest) / 5 minutes. During spring and summer, foraging activity was exclusively diurnal with 4 - 6 hours of foraging during the morning and 4 hours in the afternoon, avoiding the hotter midday. This changed to a single period of low activity concentrated during the hottest part of the day in autumn. During the hottest months, the overall daily foraging pattern appears to be complementary to its similar co-occurring congener: A. striatus daily foraging activity begins in the mornings when A. lobicornis colonies are ceasing their foraging activity cycle. Furthermore, the ending of A. striatus colonies foraging activity in the evenings also coincides with the beginning of A. lobicornis foraging. During autumn, colonies showed very scarce activity (< 15 ants / 5 minutes in any single colony). Daily and seasonal variations in nest maintenance activity were broadly similar to foraging activity patterns, though spanning larger time ranges than their foraging activity (starting earlier and finishing later).

The ants foraged within a particular temperature range that was relatively constant throughout the year and differed from its congener: A. striatus colonies foraged at higher temperatures than A. lobicornis in all seasons (26 - 45 °C vs. 16 - 35 °C, respectively).

Jofre et al. (2018) - Foraging behavior was studied in a natural reserve of San Luis, Argentina. The chaco vegetation found within the reserve had in the past been affected by overgrazing, fire, and logging. In addition to quantifying the plants selected by foragers, it was found that small nests of A. striatus harvested a greater percent of the plant species available in their foraging area and showed a higher level of selectivity than larger nests.

Male
Diploid males are known to occur in this species (found in 0.7% of 140 examined nests) (Araújo & Cavalli-Molina, 2001; Cournault & Aron, 2009).

Nomenclature

 * . Atta striata Roger, 1863a: 202 (w.q.m.) URUGUAY.
 * Combination in Atta (Oecodoma): Mayr, 1863: 458;
 * combination in Atta (Acromyrmex): Forel, 1885a: 361; Emery, 1888c: 357;
 * combination in Atta (Moellerius): Emery, 1905c: 42;
 * combination in Acromyrmex: Bruch, 1914: 217;
 * combination in Acromyrmex (Moellerius): Gallardo, 1916d: 338; Emery, 1924d: 351.
 * combination in Amoimyrmex: Cristiano, Cardoso & Sandoval, 2020: 667.
 * Status as species: Roger, 1863b: 35; Mayr, 1863: 458; Forel, 1885a: 361 (in key); Emery, 1888c: 357; Emery, 1888e: 690; Dalla Torre, 1893: 154; von Jhering, 1894: 388; Forel, 1895b: 139; Emery, 1905c: 42; Emery, 1906c: 166; Forel, 1912e: 181; Bruch, 1914: 217; Gallardo, 1916d: 338; Santschi, 1916e: 389; Emery, 1924d: 351; Santschi, 1925a: 389 (in key); Borgmeier, 1927c: 136; Kusnezov, 1953b: 338; Kusnezov, 1956: 34 (in key); Gonçalves, 1961: 129; Kempf, 1972a: 16; Zolessi & Abenante, 1977: 78; Zolessi, et al. 1988: 5; Fowler, 1988: 290; Cherrett & Cherrett, 1989: 52; Brandão, 1991: 323; Bolton, 1995b: 57; Wild, 2007b: 30.
 * Senior synonym of laeviventris: Fowler, 1988: 290; Brandão, 1991: 323; Bolton, 1995b: 57.
 * laeviventris. Acromyrmex (Moellerius) striatus var. laeviventris Santschi, 1925a: 388.
 * [First available use of Acromyrmex (Moellerius) striatus st. silvestrii var. laeviventris Santschi, 1920d: 380 (w.) ARGENTINA (Jujuy, Santa Fe); unavailable (infrasubspecific) name.]
 * Subspecies of striatus: Kempf, 1972a: 16.
 * Junior synonym of striatus: Fowler, 1988: 290; Brandão, 1991: 323; Bolton, 1995b: 55.

Karyotype


Amoimyrmex striatus shares the characteristics of both Acromyrmex and Atta, as it presents peculiarities such as its karyotype formula 2K = 20M + 2SM, indicating that A. striatus may be better classified as a genus distinct from its sibling leafcutter ants (Cristiano et al., 2013; de Castro et al., 2020). Cristiano, Cardoso & Sandoval (2020) transferred this species to the newly established genus Amoimyrmex.

References based on Global Ant Biodiversity Informatics

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