The Essential Role of Taxonomic Expertise in the Creation of DNA Databases for the Identification and Delimitation of Southeast Asian Ambrosia Beetle Species (Curculionidae: Scolytinae: Xyleborini)

Abstract

DNA holds great potential for species identification and efforts to create a DNA database of all animals and plants currently contains >7.5 million sequences representing Cognato et al. Taxonomic Expertise Improves Beetle DNA-Identification species was poor. In a demonstration of iterative taxonomy, we constructed parsimonybased phylogenies using COI and CAD sequences for two genera. Although not all clades were resolved or supported, we provided better explanations for species boundaries in light of morphological and DNA sequence differences. Confident species identifications demonstrated <3% COI and <1% CAD difference and recognition of new species became more probable when there was >10-12% COI and/or >2-3% CAD. Involvement of taxonomic experts from the start of this project was essential for the creation of a stable foundation for the DNA identification of xyleborine species. In general, their role in DNA barcoding cannot be underestimated and is further discussed.

A monograph of the Xyleborini (Coleoptera, Curculionidae, Scolytinae) of the Indochinese Peninsula (except Malaysia) and China

“…In part, this study relied on DNA based phylogenies to help resolve generic and species identities and designate species limits ( Cognato et al 2020b ). The rubric of monophyly, a sequence difference threshold, and morphological diagnostic characters provided guidance for recognizing species given sufficient specimens, for example, Xyleborus glabratus ( Cognato et al 2019 ).…”

“…1. Coptodryas Hopkins, 1915, Cryptoxyleborus Wood & Bright, 1992, Microperus Wood, 1980, Xyleborus and Xylosandrus Reitter, 1913 are likely not monophyletic ( Cognato et al 2020b ). A more robust dataset including more genes and taxa will likely help resolve the monophyly for some genera.…”

“…Several Euwallacea species were para- or polyphyletic ( Cognato et al 2020b ). These species (e.g., E. andamanensis Blandford, 1896) exhibit little morphological difference yet demonstrate > 12% COI nucleotide difference ( Cognato et al 2020b ). Morphometric analyses as with the E. fornicatus complex may be necessary to help tease out cryptic species ( Gomez et al 2018b ).…”

“…Based on this study we estimate that 30% of the species are undescribed, but given that scolytine taxonomists have not collected in many areas especially Myanmar, Laos, Cambodia, and Philippines, the number of undiscovered species is likely greater. Also, generic taxonomy will likely continue to improve with delimitation and descriptions of new genera identified among Xyleborus species ( Cognato et al 2020b ).…”

“…For most species, combinations of morphologically diagnostic characters were taken as evidence for species. In other cases, monophyly based on phylogenies derived from mitochondrial cytochrome oxidase I ( COI ) and nuclear CAD DNA sequences provided direct evidence of a species equating with an evolutionary lineage ( Cognato et al 2019 , 2020b ). Decisions to recognize monophyletic groups as species was based on the presence of morphological diagnostic characters and the demonstration of > 10% COI and > 2% CAD average pairwise uncorrected “p” distance between sister clades ( Cognato et al 2020b ).…”