Using hybridization capture to obtain mitochondrial genomes from forensically relevant North American canids: Assessing sequence variation for species identification

The majority of DNA casework processed by forensic laboratories focuses on human samples, but material from canids (dogs, wolves, coyotes) can also be encountered. Undomesticated canids can be the center of forensic investigations in the U.S. since some species are endangered. As many wolf species are similar morphologically, identification in the field by wildlife officers is not always straight-forward, making molecular based-approaches ideal. While some published methods using mitochondrial DNA targets can discriminate among Canis species, they are either not compatible with highly degraded samples or cannot differentiate closely related sub-species. Although some U.S. laboratories regularly perform veterinary/wildlife casework including canid identifications, their validated methods and reference genetic databases are not publicly available. We aimed to assess the utility of alternative regions in the mitochondrial genome for discriminating among canid species, including the complete genome. To achieve this, we utilized a commercial hybridization capture panel composed of biotinylated RNA “baits” designed for the domestic dog to enrich canid mitochondrial genomes for next-generation sequencing. We used this panel to successfully sequence complete mitochondrial genomes for 51 samples, representing four U.S. forensically relevant canids (coyote, wolf, Mexican wolf, dog). While the complete mitochondrial genome permitted discrimination, we also assessed previously published mitochondrial DNA targets (n, 5) for resolution and identified four alternate ∼200 bp fragments from ND1, ND5, COI and CYTB genes that could help resolve canids. The utility of these alternate regions should be assessed in future studies using forensic-type samples representing canids from diverse geographic areas, prior to casework implementation.