Phylogeography of the rare velvety tree ant Liometopum microcephalum (Formicidae: Dolichoderinae)

AimThe European velvety tree ant (Liometopum microcephalum), forming large colonies defending territories, has specific habitat requirements and occurs in isolated populations irregularly distributed across its range. Its dispersal is slow and colony numbers have been declining in many areas. We aim to assess the origin of populations across the species range and to reconstruct its distributional and evolutionary history. LocationFrom Italy to Israel in the south, from Czechia to Russia (Lower Volga) in the north. MethodsThree mitochondrial and one nuclear DNA markers were sequenced in 157 specimens collected at 42 sites. We constructed haplotype networks, calculated analysis of molecular variance and performed Bayesian evolutionary analysis with lineage divergence time estimations and ancestral area reconstructions. ResultsWe found 39 mitochondrial haplotypes, the nuclear marker had no variability. More than one haplotype was found within six colonies. Two groups, the European and the Asian, diverged genetically. Seven clades were delimited based on Bayesian evolutionary analysis: the Levantine, Western Anatolian, Black Sea, Northern, Balkan, Northwestern Balkan and Western. The species arose during the Pliocene and the youngest divergences within European clades occurred during the last glaciation. The Levantine clade is the basal one, the ancestral area of European populations is probably the Pannonian Basin. Main conclusionsLiometopum microcephalum is an ancient species, which speciated probably in Anatolia during the Pliocene. Although the species as such dispersed towards the northwest, reaching the Pannonian Basin, and later also the Italian Peninsula, the Levantine population stayed isolated. The European clades diverged during the Pleistocene climate oscillations, most probably during the Riss glaciation. Parts of the ancestral population survived the glaciations in the Mediterranean (Italian and Balkan Peninsulas), while others survived in extra-Mediterranean refugia (Carpathian Arc, Black Sea coast) and evolved separately for a long time. Later, the north of the Pannonian Basin was re-colonized from at least two source populations.