Abstract
Although mites (Acari) are abundant in many terrestrial and freshwater ecosystems, their diversity is poorly understood. Since most mite species can be distinguished by variation in the DNA barcode region of cytochrome c oxidase I, the Barcode Index Number (BIN) system provides a reliable species proxy that facilitates large-scale surveys. Such analysis reveals many new BINs that can only be identified as Acari until they are examined by a taxonomic specialist. This study demonstrates that the Barcode of Life Datasystem’s identification engine (BOLD ID) generally delivers correct ordinal and family assignments from both full-length DNA barcodes and their truncated versions gathered in metabarcoding studies. This result was demonstrated by examining BOLD ID’s capacity to assign 7021 mite BINs to their correct order (4) and family (189). Identification success improved with sequence length and taxon coverage but varied among orders indicating the need for lineage-specific thresholds. A strict sequence similarity threshold (86.6%) prevented all ordinal misassignments and allowed the identification of 78.6% of the 7021 BINs. However, higher thresholds were required to eliminate family misassignments for Sarcoptiformes (89.9%), and Trombidiformes (91.4%), consequently reducing the proportion of BINs identified to 68.6%. Lineages with low barcode coverage in the reference library should be prioritized for barcode library expansion to improve assignment success.
Highlights
Mites (Acari) are abundant in many terrestrial and freshwater ecosystems, their diversity is poorly understood
Most mite species can be distinguished by sequence variation in the 648 bp barcode region of the mitochondrial cytochrome c oxidase I (COI) g ene[6,7,8]
The Barcode Index Number (BIN) dataset included 7021 COI sequences derived from Canadian specimens that belonged to 189 families and four orders with an average coverage of 37 sequences (SD = 64) per family (Supplementary Table S1)
Summary
Mites (Acari) are abundant in many terrestrial and freshwater ecosystems, their diversity is poorly understood. These taxa have received more intensive DNA barcode analysis than any other national fauna[11]. Datasets based on two sequence lengths and three levels of sequence coverage for higher taxa were used to evaluate the accuracy and precision of assignments made using a distance-based identification method: BOLD ID13. From this analysis, thresholds for the identification of newly encountered mite BINs to an order and family were obtained, and the implications of their use at broader geographic scales are discussed
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