2.2 Genome survey
Genomic DNA was extracted from a single adult female of S. peregrina using SDS method (Rinkevich et al. 2006). A library with insert sizes of 400 bp was generated by Illumina TruSeq Nano DNA Library Prep Kit and sequenced to 150-nt paired end reads (PE 150 bp) on the Illumina HiSeq Xten (San Diego, CA, USA). After quality control, low-quality reads, sequencing adapters, contaminated reads and ambiguous bases were removed, whilst duplicates were filtered out. Finally, the clean data were applied to enable the genome survey and calibrate subsequent genomic assembly. Meanwhile, in order to estimate the genome size and heterozygosity of S. peregrina , we performed theK -mer distribution (K = 17) using the Jellyfish program (Marcais& Kingsford 2011).