Revision of the Plagiolepis schmitzii group with description of Pl. invadens sp. nov. – a new invasive supercolonial species (Hymenoptera: Formicidae)

Abstract

Using high-resolution stereomicroscopy and exploratory data analyses, a taxonomic revision of the cryptic species close to Plagiolepis schmitzii Forel, 1895, called Pl. schmitzii group, was conducted. Morphology was numerically recorded under highly standardised conditions considering absolute size and 16 shape, pubescence and surface characters. A key to the non-parasitic Westpalaearctic species of the ant genus Plagiolepis Mayr, 1861 is provided which firstly separates, on species group level, the Pl. pygmaea (Latreille) species group, the Pl. pallescens Forel species group and the Pl. schmitzii species group and, finally, on species level, the cryptic species of the latter group. The recognised species of the Pl. schmitzii species group are Pl. schmitzii Forel, 1895 (invasive species), Pl. barbara Santschi, 1911, Pl. atlantis Santschi, 1920 and Pl. invadens sp. nov. (invasive species) that is described as new from a supercolony in Germany. Based on morphological arguments, the taxa Pl. barbara var. madeirensis Emery, 1921, Pl. maura polygyna Santschi, 1922 and Pl. schmitzii var. tingitana Santschi, 1936 are recognised as junior synonyms of Pl. schmitzii, the taxa Pl. schmitzii crosi Santschi, 1920, Pl. pallescens var. kabyla Santschi, 1920 and Pl. perperamusSalata et al., 2018 as junior synonyms of Pl. atlantis and the taxon Pl. maura Santschi, 1920 as junior synonym of Pl. barbara. A concluding comparative section suggests that pre-adaptations for anthropogenous dispersal and transformation to supercoloniality in introduction areas are apparently common traits in Plagiolepis ants.

Ant diversity on the largest Mediterranean islands: on the presence or absence of 28 species in Sicily (Hymenoptera, Formicidae)

“…We confirm that the specimens sequenced by Degueldre et al (2021) morphologically correspond to P. schmitzii and not to any similar species considered by Seifert (2020b). The so-called P. schmitzii complex is apparently polyphyletic and Sicilian specimens belong to the same genetic clade as those from Tenerife (Canary Islands), which morphologically key out as P. schmitzii (Seifert, 2020b). In Sicily, the genus Plagiolepis is represented by the social parasites P. grassei Le Masne 1956 and P. xene Stärcke 1936, the free-living P. pygmaea (Latreille 1798) (by far the commonest Plagiolepis and one of the commonest Sicilian ants), P. pallescens Forel 1889, and P. schmitzii (Schär et al, 2020;Degueldre et al, 2021).…”

“…Records of P. schmitzii from Sicily were published by La Pergola et al (2008) and Degueldre et al (2021). We confirm that the specimens sequenced by Degueldre et al (2021) morphologically correspond to P. schmitzii and not to any similar species considered by Seifert (2020b). The so-called P. schmitzii complex is apparently polyphyletic and Sicilian specimens belong to the same genetic clade as those from Tenerife (Canary Islands), which morphologically key out as P. schmitzii (Seifert, 2020b).…”

Evolutionary history of inquiline social parasitism in Plagiolepis ants

“…It may reflect the existence of several cryptic species in the genus (Schulz and Sanetra, 2002;Kirschner et al in prerp., cf Seifert, 2018). The pallescens complex and schmitzii complex consist of at least six and four species, respectively (Seifert, 2020;Kirschner et al in prep. ).…”

“…An inquiline social parasitic lifestyle has been reported in 4 species of the ant genus Plagiolepis in Europe: in P. xene and P. grassei, both parasites of the free-living host P. pygmaea (Le Masne, 1956), as well as in P. ampeloni (Faber, 1969) and in P. delaugerrei (Casevitz-Weulersse, 2014), both found in nests of free-living species of the P. pallescens complex (previously P. taurica complex; Seifert, 2020). This complex consists of at least six Mediterranean species and a taxonomic revision using adequate data is under progress (Kirschner et al in prep.…”

“…This complex consists of at least six Mediterranean species and a taxonomic revision using adequate data is under progress (Kirschner et al in prep. ).The P. schmitzii complex includes four species, such as P. atlantis (Seifert, 2020).…”