Myrmica constricta Karavajev, 1934 – a cryptic sister species of Myrmica hellenica Finzi, 1926
Multiple evidence is presented that Myrmica constricta Karavajev, 1934 represents a cryptic sister species (= sibling species) of Myrmica hellenica Finzi, 1926: (a) males differ significantly in length of appendage pilosity, relative scape length and absolute body size; (b) a discriminant analysis (DA) and a leave-one-out-cross-validation discriminant analysis (LOOCV-DA) using 14 morphometric characters separated 90 worker nest samples of both species with a predicted error rate of 1.1 %; (c) as unsupervised method, a principal component analysis of the same data set fully confirmed this clustering; (d) Mantel tests showed a significant effect of the hypothesised con- vs. heterospecificity based on the morphological distance (OMD) as well as on the Bray-Curtis similarity index (BCSI) of worker nest samples, also when controlling for geographical distance (OMD: partial correlation r = 0.3480, p < 0.01; BCSI: r = 0.3254, p < 0.01) and hence provide a further independent argument for heterospecificity. A DA and a LOOCV-DA clearly allocated the types of M. hellenica (with p = 1.000 and p = 0.981, respectively), M. rugulosoides var. striata Finzi, 1926 (in both analyses with p = 1.000) and M. rugulosa var. rugulososcabrinodis Karavajev, 1929 (both with p = 1.000) to the M. hellenica cluster and the types of M. constricta (both with p = 1.000) to the M. constricta cluster. Hence, M. striata and M. rugulososcabrinodis are demonstrated as junior synonyms of M. hellenica. Myrmica constricta is a more western and northern species and goes north to 60°N while the Ponto-Caucasian M. hellenica does not pass 46°N. The species are sympatric in Italy and the Balkans and there are no clear suggestions for hybridisation in this area. A distribution map, comparative morphometric tables and drawings of both species are presented as well as data on colony structure, habitat selection and behaviour of M. constricta.
sibling species, cryptic diversity, numeric morphology-based alpha-taxonomy, discriminant functions