Shotgun sequencing of samples of dental calculus taken from museum specimens of Mountain, lowland, and Grauer's gorillas.

Dental calculus samples were surface -decontaminated using exposure to UV light and washing in 500 ml of 0.5M ethylenediaminetetraacetate for 1 min. DNA was extracted using a silica-based method. Double-stranded genomic libraries were prepared following the a standardized double indexing protocol. Generated libraries included double in-line barcodes to guard against index hopping. Individual libraries were purified with Qiagen MinElute columns, prior to size selection with AMPure XP beads for fragments of approximately 100-500 bp in length. The pooled library was sequenced by SciLifeLab Uppsala on 2 Illumina NovaSeq S2 flowcells using paired-end 100 bp read length and V1 sequencing chemistry.