An integrative DNA barcoding framework of ladybird beetles (Coleoptera: Coccinellidae)

Even though ladybirds are well known as economically important biological control agents, an integrative framework of DNA barcoding research was not available for the family so far. We designed and present a set of efficient mini-barcoding primers to recover full DNA barcoding sequences for Coccinellidae, even for specimens collected 40 years ago. Based on these mini-barcoding primers, we obtained 104 full DNA barcode sequences for 104 species of Coccinellidae, in which 101 barcodes were newly reported for the first time. We also downloaded 870 COI barcode sequences (658 bp) from GenBank and BOLD database, belonging to 108 species within 46 genera, to assess the optimum genetic distance threshold and compare four methods of species delimitation (GMYC, bPTP, BIN and ABGD) to determine the most accurate approach for the family. The results suggested the existence of a 'barcode gap' and that 3% is likely an appropriate genetic distance threshold to delimit species of Coccinellidae using DNA barcodes. Species delimitation analyses confirm ABGD as an accurate and efficient approach, more suitable than the other three methods. Our research provides an integrative framework for DNA barcoding and descriptions of new taxa in Coccinellidae. Our results enrich DNA barcoding public reference libraries, including data for Chinese coccinellids. This will facilitate taxonomic identification and biodiversity monitoring of ladybirds using metabarcoding.