Allopatric speciation illustrated: The hypogean genus Geotrechus Jeannel, 1919 (Coleoptera: Carabidae: Trechini), with description of four new species from the Eastern Pyrenees (Spain)

We present a study of the eastern group of species of the genus Geotrechus (Coleoptera, Carabidae, Trechini), combining molecular and morphological approaches. Four new species are described from caves of the Pyrenees of Catalonia, Spain. Two of the new species belong to the Geotrechus ubachi group sensu novo, like all the species previously known. A new group, the Geotrechus delioti group, is proposed for two new species merged until now with Geotrechus seijasi Español. The molecular study is based on a combination of fragments of four mitochondrial and two nuclear genes. We discuss the distribution of the group and provide a potential scenario of diversification, favouring the hypothesis of allopatric speciation for this old and speciose group of Pyrenean microendemic biota.