Contigs were constructed using SPAdes v3.1.0 with default parameters. Sequence variations relative to a reference genome were then determined by aligning the contigs to the reference genome using LASTZ . For each contig,we used only the highest scoring set of non-overlapping (< 100 bp) alignments. We re-mapped the reads to the contigs using BWAmem
v0.7.112 with default parameters and obtained coverage and quality data for each site using mpileup in samtools v1.1 Variant sites were reported if they were associated with mutations or indels in the LASTZ alignment and were not removed due to any of the filters listed below.