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 centers 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 . The formation of two disjunct centers 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 is much older than the generally assumed date (Pleistocene: ca. 3 MYA) for the formation of the Isthmus of Panama.
The phylogenetic relationships of the genera of Epipsocetae were inferred on the basis of 122 morphological characters of adult specimens, corroborating the monophyly of the group with ten synapomorphies. The genera are grouped in well defined clades consistent at family level. Dolabellopsocidae, Ptiloneuridae and Epipsocidae are recognized as monophyletic families. In each family, the genera appear as monophyletic units, except in Epipsocidae, where the relationships are ambiguous and monophyly of most genera is not supported. Results indicate that Cladiopsocidae is paraphyletic; it was divided into two monophyletic families: Spurostigmatidae and Cladiopsocidae (sensu stricto), represented by the genera Spurostigma and Cladiopsocus respectively. Neurostigma is recognized as a monophyletic genus closely related to other epipsocid genera, nevertheless due to the low resolution obtained within Epipsocidae, it is not possible to decide if it is a genus of that family or if it forms a different clade at family level. The genera Parepipsocus Badonnel, previously considered as incertae sedis, and Dimidistriata Li & Mockford, previously placed tentatively in Dolabellopsocidae, are included in Epipsocidae. Loneuroides, Terryerwinia and Timnewia are recognized as valid genera. Two well defined clades are recognized within E pipsocidae, one with exclusively American genera, and the other that includes Asiatic and American genera.
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