A revision of the Palaearctic species of the ant genus Cardiocondyla Emery 1869 (Hymenoptera: Formicidae).

A synopsis of the Palaearctic species of the ant genus Cardiocondyla Emery 1869 is provided. The four species groups which are of Palaearctic origin or which are restricted in their distribution to this faunal zone, the C. elegans, C. ulianini, C. batesii and C. stambuloffii group-consisting of 25 recognized species-are taxonomically revised. Further nine species belonging to species groups of Ethiopic and Oriental origin which may penetrate into and build up true outdoor populations in the southern Palaearctic are only treated in the determination key. The main working rationale of this revision is Numeric Morphology-Based Alpha-Taxonomy (NUMOBAT) with formation of species hypotheses largely based on exploratory data analyses and checking these hypotheses by discriminant analysis. NUMOBAT data of the species considered comprise 727 worker samples with 1555 individuals and 23,300 primary data. Including high-resolution photos of surface microstructures, all species are depicted by z-stack imaging in four standard visual positions. Numeric data on 19 phenotypical characters are presented in comparative tables and supplementary verbal descriptions are given. In contrast to species groups with Ethiopian, Oriental and Australasian origin, no member of the four Palaearctic species groups has developed a tramp species potential to spread globally. Four cryptic species are described as new: Cardiocondyla dalmaticoides n. sp., C. caspiense n. sp., C. verdensis n. sp. and C. rolandi n. sp. Confirmed were the synonymies of Cardiocondyla elegans santschii Forel 1905, C. provincialis Bernard 1956 and Xenometra gallica Bernard 1957 with C. elegans Emery 1869, that of C. elegans eleonorae Forel 1911 with C. bulgarica Forel 1892, that of C. elegans torretassoi Finzi 1936 with C. nigra Forel 1905, and that of C. bogdanovi Ruzsky 1905, C. montandoni Santschi 1912 and C. stambuloffii taurica Karavajev 1927 with C. stambuloffii Forel 1892. Cardiocondyla bicoronata Seifert 2003 was newly synonymized with C. nigra Forel 1905.