Three Turano-European species of the Temnothorax interruptus group (Hymenoptera: Formicidae) demonstrated by quantitative morphology.

The ant genus Temnothorax is very diverse in the Palaearctic region. It consists of many cryptic species which are hard to discover with conventional toolkits of alpha taxonomy. However, the modern, quantitative morphological approaches have been improved, and their increased accuracy and taxonomic specificity allow taxonomists to discover cryptic biological diversity on a much finer scale. In this paper, we provide quantitative morphology-based evidence in support of our contention that the Turano-European Temnothorax interruptus (Schenck, 1852) is, in fact, a complex of three clearly separable lineages. Species hypotheses are developed through NC-PART clustering, a highly automated protocol using two algorithms, NC-clustering and Partitioning Based on Recursive Thresholding (PART). Our results are based on a large dataset generated from 19 continuous morphometric traits measured on a total of 165 workers from 66 nest samples. Classifications returned by the exploratory analyses are confirmed by cross-validated Linear Discriminant Analysis (LOOCV-LDA) with a 0.6% error rate in 166 workers. Two known type series, Temnothorax interruptus (Schenck, 1852) and Leptothorax tuberum ssp. knipovitshi Karavaiev, 1916, which meet the criteria for this species complex, are nested in the same cluster, and each classification is supported with posterior p = 1.0. Therefore, Leptothorax tuberum ssp. knipovitshi is considered a junior synonym of T. interruptus. The two other morphological clusters are described as T. morea sp.n. and T. strymonensis sp.n. Syntopic occurrence has been found in only one case, between Temnothorax interruptus and T. strymonensis, and mixed colonies were not observed. Temnothorax interruptus has been identified as a Turano-European species, with distribution from Spain to the Caucasus but completely unknown in the Mediterranean region. The two broadly sympatric East Mediterranean species, T. morea and T. strymonensis, occur widely in the region from Croatia to Turkey.