Phylogeography and taxonomic status of the Formica picea complex (Hymenoptera: Formicidae)

The black bog ant Formica picea complex is widespread from the Atlantic to the Pacific coasts of Eurasia. This complex was earlier believed to consist of one or two species (F. picea and F. candida). However, molecular analysis suggested that it includes three cryptic species. One is F. picea from Europe, another, F. candida, is currently known exclusively from Kyrgyzstan, while the third one, temporarily designated here as Formica sp., inhabits the easternmost part of Eurasia from China to Kamchatka. It is unknown how F. picea and Formica sp. are distributed in Siberia and whether their ranges intersect. Here we studied a sample of this complex from Siberia using mtDNA and found that their ranges overlap. The distribution of Formica sp. extends from the south of West Siberia, including Altai, to China, and the Russian Far East. No phylogeographic structure was detected, suggesting their recent dispersal from a single source. F. picea was found as far as East Siberia, but was relatively rare. While the European and West Siberian populations were genetically closely related, the specimens from Zabaykalsky Krai differed, suggesting a putative East Siberian refugium. We also determined that ecologically F. picea inhabits peat bogs in lowland areas and grassy communities above the tree line in the European mountains; in Altai, it is found in mountain steppes, while in Transbaikalia, in waterlogged areas along riverbanks. Formica sp. thrives in dry steppes and low riverbanks, but avoids bogs. Thus, F. picea and Formica sp. differ genetically, and have different distribution ranges, as well as habitat preferences. This supports the opinion that Formica sp. should be recognized as a distinct species.