Euscorpius sicanus (Scorpiones: Euscorpiidae) from Tunisia: DNA barcoding confirms ancient disjunctions across the Mediterranean Sea

We used a DNA barcoding marker (mitochondrial cox1) to investigate the controversial natural occurrence of Euscorpius sicanus (C.L. Koch) in North Africa. We tested this hypothesis by comparing a sample collected from a mountain in Tunisia to disjunct populations in Sardinia, Malta, and Greece. Using these samples, and a few additional Euscorpius spp. from southern Europe as outgroups, we reconstructed the maternal phylogeny. We then used a molecular clock to place the phylogeny in a temporal context. The Tunisian sample grouped closest to a specimen from Sardinia, with both being more distantly related to E. sicanus from Malta, which is known to be genetically similar to samples from Sicily. Molecular clock estimates suggest an ancient disjunction across the Mediterranean Sea, with the divergence between samples from Sardinia and Tunisia estimated to have occurred between the Late Miocene and late Pliocene. The divergence date (mean = 5.56 Mya) closely corresponds with the timing of a sudden refilling of the Mediterranean Sea after it had evaporated during the Messinian salinity crisis. This rapid influx of water, in conjunction with tectonic activity, could have sundered connections between Euscorpius in North Africa and what is now the island of Sardinia. These results provide yet another case in which DNA barcodes have proven useful for more than just identifying and discovering species.