A taxonomic revision of the members of the Camponotus lateralis species group (Hymenoptera: Formicidae) from Europe, Asia Minor and Caucasia

A taxonomic revision of the Camponotus lateralis group based on methods of Numeric Morphology-Based Alpha-Taxonomy (NUMOBAT) is presented considering the Palaearctic region west of 46°E. One size, nine shape and three setae characters were recorded in a total of 260 samples with 587 worker individuals. Species hypotheses were formed by three exploratory data analyses: the hierarchical methods NC-Ward and NC-part.hclust and the iterative vector-quantization method NC-part.kmeans. Samples with classifications disagreeing among the methods were finally allocated to a particular cluster by wild-card runs in a controlling linear discriminant analysis. Results: The taxonomy of the C. lateralis group is complicated by the superimposition of three types of intraspecific polymorphism: (a) minor vs. major worker size dimorphism, (b) polymorphism of pigmentation pattern and (c), in at least one species, extreme dimorphism of shape and setae characters independent from size. A two-step cluster analysis and principal component analysis considering head and scape length indices and absolute size resulted in fully coincident separations of minors and majors with a general rule applicable for a collective of four long-headed and another rule applicable for a collective of four short-headed species. The identity of 42 taxa was evaluated on the basis of original descriptions and type specimens to exclude a junior synonymy of the taxon introduced here. A key is provided for nine valid species occurring in the area of Europe, Asia Minor and Caucasus: Camponotus lateralis (Olivier 1792), C. piceus (Leach 1825), C. atricolor (Nylander 1849), C. dalmaticus (Nylander 1849), C. candiotes Emery 1894, C. rebeccae Forel 1913, C. anatolicus Karaman & Aktac 2013, C. honaziensis Karaman & Aktac 2013 and C. heidrunvogtae sp. nov. The latter is restricted to a 120 000 km² area of the Balkans. Camponotus ebneri Finzi 1930 (stat. nov.) from Lebanon was raised to species level and is considered as sister species of C. dalmaticus. Seven taxa from North Africa, the Canaries and Middle East, showing a lot of similarities with species of the C. lateralis group, were excluded to represent synonyms of one of the ten aforementioned valid species. Further, seven Camponotus taxa from Europe, Asia Minor and the Middle East were clearly excluded from the C. lateralis group. Camponotus melanogastes (Latreille 1802), Camponotus axillaris (Spinola 1808), C. merula (Losana 1834) (syn. nov.), C. armouri Wheeler 1926, C. lateralis balearis Santschi 1929 (syn. nov.), C. lateralis purius Santschi 1929 (syn. nov.) and C. kosswigi Donisthorpe 1950 are synonymized under C. lateralis. Camponotus foveolata (Mayr 1853), C. ebeninus Emery 1869 (syn. nov.), C. piceus st. spissinodis var. dusmeti Santschi 1932 and C. figaro Collingwood & Yarrow 1969 (syn. nov.) were synonymized under C. piceus, C. lateralis var. cypridis Santschi 1939 (syn. nov.) under C. rebeccae and C. lateralis var. rectus Forel 1892 under C. atricolor. Due to insufficient original descriptions and missing types, there is no chance to conclude on either the specific, generic or tribal identity of six taxa supposed by previous authors of belonging to the C. lateralis group. These taxa – Formica bicolor Latreille 1798, Formica pallidinervis Brulle 1833, Camponotus hemipsila (Forster 1850), Camponotus sicheli Mayr 1866, Camponotus kiesenwetteri angustatus Forel 1889, and Camponotus lateralis var. rhodia Santschi 1934 – were listed under Incertae Sedis.