Plagiolepis schmitzii Forel, 1895

Bernhard, Seifert, 2020, Revision of the Plagiolepis schmitzii group with description of Pl. invadens sp. nov. - a new invasive supercolonial species (Hymenoptera: Formicidae), Deutsche Entomologische Zeitschrift 67 (2), pp. 183-196 : 183

Plagiolepis schmitzii Forel, 1895

Plagiolepis pygmaea var. schmitzii Forel, 1895 Published type locality: "Serra d’Agua, Madeira (Seminardirektor P. E. Schmitz)" [32.727°N, 17.027°W, 347 m alt.]. Nine paratype workers were investigated from MHN Genève collected by Schmitz in at least three localities in Madeira. Amongst these were workers pictured in AntWeb (2020), labelled " Pl. pygmaea Latr. v. Plagiolepis schmitzii For. Garajau Madeira Schmitz 3, 5-9", "ANTWEB CASENT0909859". All investigated specimens do not carry a label pointing to Serra d’Agua. I also investigated the lectotype gyne labelled " Pl. pygmaea Latr. v. Plagiolepis schmitzii For. Madeira (Schmitz)", "ANTWEB CASENT0909858", "LECTOTYPE (upper) Plagiolepis pygmaea var. schmitzi Forel, 1895 desig. Wetterer & Espadaler".

Plagiolepis barbara canariensis Plagiolepis barbara var. canariensis Santschi, 1920 [syn. Plagiolepis schmitzii ] Described from Tenerife: La Laguna, Bejano and Esperanze. No type specimens or figures of this taxon were available and the descriptive statements of Santschi are useless. A junior synonymy with Pl. schmitzii appears probable for zoogeographic reasons.

Plagiolepis barbara madeirensis Plagiolepis barbara var. madeirensis Emery, 1921 [syn. Plagiolepis schmitzii ] Identification by evaluation of photos of a type worker in AntWeb (2020) labelled " Pl. barbara var. Plagiolepis barbara madeirensis Em.", "SYNTYPUS Plagiolepis barbara var. Plagiolepis barbara madeirensis Emery, 1921", "Funchal Madeira De Guerne", "ANTWEB CASENT0905140".

Plagiolepis maura polygyna Plagiolepis maura polygyna Santschi, 1922 [syn. Plagiolepis schmitzii ] Four type workers were investigated from NHM Basel labelled "Tunisie, Cheri Chera 27 III 21 Santschi".

Plagiolepis schmitzii tingitana Plagiolepis schmitzii var. tingitana Santschi, 1936 [syn. Plagiolepis schmitzii ] Santschi published as collecting sites "Tanger w. (type) et Volubilis w. (Alluaud)". Four type workers were investigated from NHM Basel labelled "Tanger Ch. Alluaud".

Material examined.

A total of 21 samples with 64 workers were subject to morphometric investigation.

Algeria: Mascara, 1926 [35.398°N, 0.138°E, 594 m alt.] . England: Isle of Wight: Bonchurch , 2007.06.21 [50.59°N, 1.19°W, 3 m alt.] . Germany: Schkeuditz, 2019.02.11 [51.392°N, 12.204°E, 104 m alt.]; Schriesheim, 2017.05 [49.470°N, 8.46°E, 118 m alt.]; Seligenstadt , 2009.04 [50.045°N, 8.975°E, 115 m alt.] . Morocco: Chefchaouen, 2009.03 [35.183°N, 5.300°W, 400 m alt.]; Meknes , 1940.02.02 [33.894°N, 5.547°W, 551 m alt.]; Rabat (Santschi) [33.973°N, 6.845°W, 84 m alt.]; Tanger (Alluaud), type Pl. schm. tingitana [35.755°N, 5.819°W, 30 m alt.]; Tiz-n-Test - 8 km N, 1987.05.05, No 13015 [30.889°N, 8.370°W, 1810 m alt.] . Netherlands: Brakel, 2013.02 [51.820°N, 5.093°E, 2 m alt.]; Tholen , 2011.05.27 [51.539°N, 4.217°E, 1 m alt.]; Utrecht, 2006.09.09 [52.09°N, 5.12°E, 10 m alt.] . Portugal: Madeira: Estreito da Calheta , 2009.03 [32.733°N, 17.167°W, 350 m alt.]; Madeira, 1400 m (Schmitz), paratypes Pl. schmitzii [33.0°N, 17.0°W, 1400 m alt.]; Madeira: Garajau (Schmitz), paratypes Pl. schmitzii [32.64°N, 16.85°W, 230 m]; Madeira: Palheiro (Schmitz), paratypes Pl. schmitzii [32.65°N, 16.87°W, 360 m alt.] . Spain: La Palma: Todoque, 2010.03.02 [28.617°N, 17.903°W, 334 m alt.]; Tenerife : Las Canadas NP, 1999.06.02 [28.26°N, 16.61°W, 2300 m alt.]; Sevilla , 2019.06.24 [37.394°N, 5.994°W, 10 m alt.] . Tunisia: Cherichara , 1921.03.27, types Pl. polygyna [35.637°N, 9.815°E, 255 m alt.] .

Diagnosis and taxonomy

(Table 1 , key, AntWeb, 2020: CASENT0906252, Figs 2 - 4 ):

Pl. schmitzii has the longest scape and funiculus segments within the species group. The most similar species is Pl. atlantis , whereas Pl. barbara and Pl. invadens sp. nov. appear more distant and have much shorter scapes (for their status, see there). The material allocated here to Pl. schmitzii (21 samples, 64 specimens) and Pl. atlantis (20 samples, 56 specimens) were investigated by exploratory data analyses (EDAs). Considering absolute head size and all 16 allometrically-corrected shape, pubescence and surface characters, NC-Ward, NC-part.kmeans, NC-NMDS-kmeans, a principal component analysis (PCA) and NC-part.hclust confirmed two clusters. The classification of the first four EDAs agreed for each of the 41 samples, whereas NC-part.hclust exposed two samples as indeterminate outliers (Fig. 5 ). If these two samples were run as wild-cards in a controlling linear discriminant analysis (LDA), they were classified in agreement with the first four EDAs. The classification error of the LDA on an individual level was 0.7 % in 120 workers. All these data are a clear indication of separate species identity of Pl. schmitzii and Pl. atlantis . Running the type series of seven taxa as wild-cards in the LDA resulted in clear allocations to either cluster. The posterior probabilities for allocation to the Pl. schmitzii cluster were 1.000 in each of the three paratype series of Pl. schmitzii from Madeira, 0.999 in the type series of Pl. polygyna and 1.000 in the type series of Pl. tingitana , whereas the posterior probabilities for allocation to the Pl. atlantis cluster were 1.000 in the type series of Pl. atlantis , 0.916 in the type series of Pl. crosi , 0.994 in the type series of Pl. kabyla and 0.998 in the type series of Pl. perperamus . All five EDAs allocated any type series in agreement with the LDA wild-card runs. As a consequence, Pl. polygyna and Pl. tingitana are junior synonyms of Pl. schmitzii , whereas Pl. crosi , Pl. kabyla and Pl. perperamus are junior synonyms of Pl. atlantis . Without types of Plagiolepis barbara var. madeirensis Emery, 1921 being available, the synonymisation of this taxon with Pl. schmitzii is highly probable for two reasons: (1) the scape is very long: the data of SL and CW, as they can be derived with minimum distortions from the CASENT0905140 photo of the Pl. b. madeirensis type, are within the Pl. schmitzii cluster and outside the cluster formed by Pl. atlantis , Pl. invadens sp. nov. and Pl. barbara ; (2) Madeira seems to be inhabited by only a single, very abundant Plagiolepis species which is to be named Pl. schmitzii .

Distribution and biology.

According to direct investigation of voucher specimens, Pl. schmitzii is distributed from Madeira and the Canaries across West Mediterranean Africa east to Tunisia. There are anthropogenous introductions north of 46°N. In Germany, it has been found so far only in houses, with workers occasionally foraging outdoors. However, year-round outdoor nesting has been recently reported from two sites in the Netherlands (Jinze Noordijk pers. comm. 2020). Accordingly, there is a clear potential for becoming an established neozoon in NW and Central Europe in the context of global warming. Polygyny and polydomy with colony territories over several houses is confirmed for populations in the Netherlands and Germany. The population from Madeira, Estreito da Calheta is obligatory polygynous and highly polyandrous (a queen may have up to 14 different mates), whereas the population from Chefchaouen in Morocco is facultatively polygynous and moderately polyandrous ( Thurin et al. 2011). These authors stated that relatedness within colonies remains high because of sib-mating and relatedness of the male mates of a queen (fixation index F it = 0.24 in the Madeiran and 0.26 in the Moroccan population). Small size, polygyny with intranidal mating and broad food spectrum are pre-adaptations for a career as a tramp species. Pl. schmitzii is everywhere present in Madeira and rivals there in abundance with Lasius cf. grandis Forel.

Figures

Figure 2. Head of a worker of Plagiolepis schmitzii (image from AntWeb, 2020: CASENT 0906252, photographer E. Ortega).

Figure 4. Dorsal aspect of a worker of Plagiolepis schmitzii (image from AntWeb 2020: CASENT 0906252, photographer E. Ortega).

Figure 5. Results of four variants of NC-clustering: NC-Ward (hierarchical, tree shown), NC-part. hclust (hierarchical), NC-part. kmeans (iterative vector-quantisation), NC-NMDS (non-metric scaling); 21 nest samples of Plagiolepis schmitzii (grey bars) and of 20 nest samples of Pl. atlantis (black bars). Outliers in NC-part. hclust are given by the white gap.