mitochondrial genomes

Total genomic DNA was extracted using the Ezup Column Animal Genomic DNA Extraction Kit (B518251; Sangon Biotech, Shanghai, China) according to its instruction. A second-generation sequencing library was constructed for each sample with a starting DNA material of 300-1000 ng according to Meyer and Kircher and Li et al. Briefly, the DNA samples were sheared to about 250 bp using a Covaris M220 ultrasonicator (Covaris, Inc., MA, USA). The fragmented DNA samples were checked using electrophoresis with a 1.5% agarose gel. The library construction process include end repair, ligation and fillin Meyer and Kircher (2010) and Li et al. (Li et al. 2013). After amplification, the library products of all samples were mixed in equimolar, and DNA fragments larger than 1 kb were removed by gel extration. The recovered samples were sequenced on an Illumina HiSeq platform with 2x150 paired-end configuation at Genewiz (Suzhou, China).