Multiple trans-Beringia dispersals of the barklouse genus Trichadenotecnum (Insecta: Psocodea: Psocidae)

The causes underlying disjunct distributions are of major importance in biogeography. Arcto-Tertiary relict biotas in the temperate northern hemisphere, which typically show disjunct distributions between Asia and the Nearctic region, are widely known, but often poorly understood examples of disjunct distributions. The distributional pattern of the barklouse genus Trichadenotecnum is an example of an Arcto-Tertiary relict, with centres of species diversity in Asia and Central America. We evaluated the potential causes of this disjunct distribution in Trichadenotecnum using a molecular phylogeny, divergence dating and ancestral area reconstruction. Phylogenetic analysis identified three separate clades of New World Trichadenotecnum, whereas all other groups were distributed in the Old World. Ancestral area and dating analyses recovered three independent events of trans-Beringian dispersal in the Oligocene to Miocene (27–15 Mya). The formation of two disjunct centres of diversity can be explained by the restriction of distributional areas to temperate refugia during the Quaternary glaciations (2.5–0.02 Mya). The South American Trichadenotecnum appeared to have arisen from two independent dispersal events in the Miocene (19–9 Mya). These estimated dispersal dates are much older than the generally assumed date (Pleistocene: c. 3 Mya) for the formation of the Isthmus of Panama.