Seifert, B., Schultz, R., Ritz, M.S. & Ritz, C.M.

Cryptic species of the Myrmica tibetana complex (Hymenoptera: Formicidae) revealed by integrative taxonomy

Three closely related species, Myrmica tibetana Mayr, 1889, M. bactriana Ruzsky, 1915 and M. gebaueri sp.n., are identified. They are restricted to the Tibetan Plateau and proposed to form the M. tibetana species complex. Myrmica tibetana and M. gebaueri sp.n. are truly cryptic: They showed considerable interspecific overlap in all of the tested 18 shape, pilosity, and sculpture characters and were not safely separable by simple visual inspection by a trained expert. However, all three entities are clearly demonstrated by Nest Centroid (NC) clustering of morphological data which agreed by 100% with the genetic classification based on 11 microsatellite markers. The clusters shown by hierarchical NC-Ward clustering and the partitioning algorithms NC-part.hclust and NC-part.kmeans were coincident in all of the 62 nest samples. A stepwise linear discrimiant analysis reducing the set to nine characters achieved a classification error of 0% in 178 investigated worker individuals. All three entities are partially sympatric, and the absence of phenotypically mixed nest samples rejects the hypothesis that they could represent an intraspecific polymorphism. The coincident classification of all three exploratory data analyses of morphology and nuDNA revealed a paraphyly of mtDNA between M. bactriana and M. gebaueri sp.n. adding another example to the multiple evidence on failures of mtDNA barcoding in biodiversity research. Yet, mtDNA data appeared adequate for rough assessment of divergence times. According to this, the separation of the M. tibetana complex from other members of the M. rubra group is estimated to have occurred approximately 7.5 Ma Before Present (BP), and the radiation within the M. tibetana complex started > 5 Ma BP. A taxonomic description and a differential diagnosis of M. gebaueri sp.n. are presented. Myrmica bactriana Ruzsky, 1915 is shown as a senior synonym of M. furva Ruzsky, 1915 and M. ruzskyana Radchenko & Elmes, 2010. Synonymies of either member of the M. tibetana complex with the following Central and Middle Asian species are excluded: M. smythiesii Forel, 1902, M. fortior Forel, 1904, M. wittmeri Radchenko & Elmes, 1999, and M. tenuispina Ruzsky, 1905.