The Case for a Nuclear Barcode: Using the CAD CPS Region for Species and Genus Level Discrimination in Beetles

DNA barcoding has revolutionized how we discover, identify, and detect species. A substantial foundation been established with millions of mitochondrial cytochrome c oxidase I sequences freely available for eukaryotes. However, issues COI ranging from uniparental inheritance small genetic population sizes to nuclear asymmetric introgression can impede its use. We propose using CAD as the “nuclear barcode” complement barcode ameliorate these concerns. focused on beetles taxonomically diverse species-level studies that used CAD. An ambiguous gap was present between intra- interspecific distances in COI; this led difficulty automated detection methods. found pseudogenes, problematic structure, introgression, incomplete lineage sorting represented data. gene tree illuminated cryptic problems. Placement tests species outgroups distance-based building were largely successful CAD, demonstrating phylogenetic signal at genus levels. Species placement typically unique one locus, allowing recognition misdiagnosis. conclude a is valuable tool beetle diagnostics, metabarcoding, faunistic surveys.