Camponotus atricolor

This species is mainly distributed in southern and central Europe and in the southern part of eastern Europe (Seifert 2007) and Turkey. It is a xerothermophilous species living mostly in open, dry grasslands, with nests built in the ground. Workers are highly polymorphic. (Marko et al., 2009)

Identification
Seifert, 2019: Differential characters of C. atricolor against other blackish species of the group, which are detectable by subjective eye inspection, are the shallow, sometimes nearly absent, metanotal depression, the roughly linear dorsal mesosomal profile and the missing extension of large scape diameter near to its base. However, due the negative allometry of scape base extension, this structure may be missing in large workers of the other four species.

Distribution
Marko et al. (2009) - In Romania the occurrence of C. atricolor is reported only from Dobrogea region near the Black Sea (Forel 1906) and from Comana, Giurgiu County, southern Romania (Montandon and Santschi 1910). More recently Gallé et al. (2005) also mention the occurrence of intermediate C. piceus/atricolor specimens from Munar and Bezdin (Secusigiu village), Arad County, western Romania, while reporting the occurrence of C. atricolor sensu Seifert (2007) in the bordering Hungarian region. Based on personal collections from the same region we can also confirm the occurrence of C. atricolor sensu Seifert (2007) in Arad County, although the morphometric data prove its intermediate state: 6 worker, Nădab, Arad County, RO, 20.05.2007, leg. B. Markó, mean PW/PL = 0.739 (±0.06), mean PEW/MW = 0.53 (±0.027).

Seifert, 2019: Steppe zones of Caucasian lowlands, the south of European Russia and the Ukraine, Balkans, Hungary, E Austria and S Moravia (here the northernmost confirmed site at 49.0°N). There is a strong range overlap with Camponotus piceus on the Balkans and some overlap with Camponotus candiotes in the Caucasus.

Distribution based on Regional Taxon Lists
Palaearctic Region: Austria, Bulgaria, Greece, Hungary, Romania, Russian Federation.

Castes
Seifert, 2019: A minor worker is depicted in AntWeb.org under CASENT0179869 and a major worker under CASENT0179870.

Nomenclature

 * atricolor. Formica atricolor Nylander, 1849: 36 (w.) RUSSIA.
 * Combination in Camponotus: Roger, 1863b: 1.
 * Combination in C. (Myrmentoma): Emery, 1925a: 67; Emery, 1925b: 120.
 * Junior synonym of lateralis: Mayr, 1855: 322; Nylander, 1856b: 58; Smith, F. 1858b: 12 (first entry, see below); Mayr, 1863: 399; Roger, 1863b: 1; André, 1874: 201 (in list); Forel, 1874: 97 (in list); Emery & Forel, 1879: 448.
 * Subspecies of lateralis: Forel, 1874: 40; Forel, 1892i: 306; Forel, 1894d: 41; Emery, 1896d: 373 (in list); Ruzsky, 1902d: 7; Ruzsky, 1903b: 302; Forel, 1904b: 380; Ruzsky, 1905b: 254; Forel, 1906c: 189; Forel, 1911d: 355; Emery, 1914d: 159; Wheeler, W.M. & Mann, 1916: 174; Karavaiev, 1926e: 193; Kuznetsov-Ugamsky, 1929b: 36.
 * Subspecies of piceus: Emery, 1925a: 67; Karavaiev, 1927a: 295; Karavaiev, 1927c: 277 (in key).
 * Subspecies of merula: Novák & Sadil, 1941: 109 (in key).
 * Junior synonym of merulus: Bernard, 1967: 344.
 * Status as species: Smith, F. 1858b: 12 (second entry, see above); Arnol'di & Dlussky, 1978: 552; Agosti & Collingwood, 1987b: 283 (in key); Seifert, 2007: 155 (in key); Borowiec, L. & Salata, 2012: 472; Borowiec, L. 2014: 27; Seifert, 2019: 23.
 * Senior synonym of rectus: Emery, 1896d: 373; Emery, 1925a: 70; Karavaiev, 1936: 191.
 * Junior synonym of piceus: Dalla Torre, 1893: 238; Karavaiev, 1936: 190 (redescription); Atanassov & Dlussky, 1992: 222; Bolton, 1995b: 87; Radchenko, 1997b: 706; Radchenko, 2007: 37; Legakis, 2011: 28; Radchenko, 2016: 334.

Type Material
Seifert, 2019: Investigated were three syntypes of Camponotus atricolor on three different pins labeled ‘Ross.mer. \ Motschulsky 22\ Coll. Nyland \ Motschulsky \ Mus.Zool H:fors Spec. typ. No 5086 Formica atricolor Nyl’, FMNH Helsinki. The syntypes have identical labels except for ‘Spec. typ. No’ which is 5087 and 5088 in the other two specimens.

Seifert, 2019: There is no material in the or  collection that can be reliably identified as type material for Camponotus lateralis rectus.

Taxonomic Notes
Marko et al. (2009) - This species has a controversial status. Atanassov and Dlusskij (1992) synonymized it with Camponotus piceus due to their findings of intermediate morphs between the two species concerning the depth of the mesopropodeal furrow. A. Radchenko (pers. comm.) also supports this hypothesis on the basis of type material investigation of C. atricolor. Thus, several authors treat it as junior synonym of C. piceus (Radchenko 1997a, Bolton et al. 2006, Werner and Wiezik 2007), while other specialists consider it a valid species (Steiner et al. 2002, Gallé et al. 2005, Seifert 2007). This morph shows clear differences from C. piceus in characters other than just the depth of mesopropodeal furrow (see also Emery 1925), suggesting Camponotus crypsis. Further investigation should elucidate the taxonomic status of the ‘atricolor’ morph.

Seifert, 2019: C. atricolor has been raised to species level by Seifert (1996) and Seifert (2007) but this view did not receive much appreciation by other myrmecologists. It is apparent that C. atricolor, C. piceus and C. candiotes are closely related but only the latter two represent truly cryptic species. The exploratory data analyses NC-part. hclust, NC-part.kmeans and NC-Ward provide a clear separation of C. atricolor from the cluster of siblings formed by C. piceus and C. candiotes. Considering CS and all 12 RAV-corrected shape and seta characters, the error rate on the K = 2 level (atricolor vs. piceus+candiotes) in 124 examined samples is 0 % in NC-part.hclust, 2.4 % in NC-part.kmeans and 0 % in NC-Ward (Fig. 12). The three samples misclassified by NC-part.kmeans were rectified by the controlling LDA if run as wild-cards. The mean error rate of the three exploratory data analyses of 0.8 % is clearly below the 4 % threshold recommended by the Pragmatic Species Concept (Seifert 2014). Thus we have a strong justification for the species status of C. atricolor (see also discussions for Camponotus candiotes and Camponotus piceus).

This clear result on the nest sample level is confirmed by analyses on individual level. The classification error by a LDA considering the five blackish species given in Tab. 3 is only 1.3 % in 77 worker individuals of C. atricolor and 0.8 % in 357 individuals of all five species. The corresponding errors in a leave-one-out cross-validation LDA are 1.3 % and 1.4 % respectively.

Seifert, 2019: The three syntype workers of C. atricolor are allocated to C. atricolor with mean p = 1.0000 if run as wild-card in a 5-class LDA considering the five black species of the group given in Tab. 3.

Seifert, 2019: Forel gave as sampling sites the Bulgarian Black Sea towns ‘Anchialo’ (today named Pomorje) and ‘Sozopolis’ (today Sozopol) and Forel’s description of the mesosomal shape strongly suggests a synonymy with C. atricolor. This view is supported by the fact that C. atricolor is by far the most abundant of the black species along the western coast of Black Sea. Four investigated workers of topotypical material from Sozopolis in the Forel collection in (possibly types which Forel missed to designate) are allocated to C. atricolor with a mean posterior probability of p = 0.9975 if run as wild-card in a 5-class LDA considering the five black species given in Tab. 3.