High-throughput sequencing data analysis
Mt-genome assembly was conducted with the Geneious 11.1.3 package (https://www.geneious.com/). First, demulitplexed raw sequence reads were trimmed and quality-filtered with BBDuk 37.64 of the BBTools package (https://jgi.doe.gov/data-and-tools/bbtools/) and duplicate reads were removed with Dedupe 37.64 (BBTools package); for both steps we applied standard settings. For mt-genome assembly, cleaned reads were mapped onto the reference mt-genome of L. europaeus (GenBank: NC_004028.1) using the Geneious assembler with standard settings. Newly produced mt-genomes were manually checked and then annotated with Geneious. For phylogenetic tree reconstruction, we added additional mt-genome sequences from EBHs from Sweden, Poland, Greece, Cyprus and Turkey available in GenBank and aligned them as described above. Tree reconstructions based on the maximum-likelihood algorithm and Bayesian inference were performed as described above using IQ-TREE and MrBayes software.