Evidence for the Pleistocene persistence of Collembola in Great Britain

Aim: Using two genera of springtail, Lepidocyrtus and Entomobrya (Collembola), we test for genetic signatures of Pleistocene persistence of soil arthropods in Great Britain. Location: Great Britain. Methods: A region of the mitochondrial cytochrome oxidase I (COI) gene was sequenced for 1,150 Collembola specimens from the genera Lepidocyrtus and Entomobrya across Great Britain. Individuals were clustered into Operational Taxonomic Units (OTUs), and both OTU richness and geographical patterns of genetic variation within OTUs were compared between glaciated and unglaciated areas to identify signatures of OTU persistence through Pleistocene glacial events. Results: Our analyses identified 12 Entomobrya and 18 Lepidocyrtus OTUs in Great Britain. Lepidocyrtus OTU richness was significantly lower in glaciated than unglaciated areas, whereas there was no difference for Entomobrya OTU richness. However, both genera presented clear patterns of geographically disjunct genetic variation and geographically localized diversification of OTUs. Estimated dates for the onset of in situ diversification events indicate population persistence that pre-dates the Last Glacial Maximum. Main conclusions: Patterns of genetic diversity within Collembola OTUs in Great Britain add to a growing body of evidence that elements of the invertebrate fauna have persisted in situ through Pleistocene glacial cycles. Genetic signatures of population persistence in more northern glaciated areas of Great Britain support a hypothesis of geothermal glacial refugia that call for further investigation with other soil mesofaunal taxa.