Abstract
The subfamily Denticollinae is a taxonomically diverse group in the family Elateridae. Denticollinae includes many morphologically similar species and crop pests, as well as many undescribed species at each local fauna. To construct a rapid and reliable identification system for this subfamily, the effectiveness of molecular species identification was assessed based on 421 cytochrome c oxidase subunit I (COI) sequences of 84 morphologically identified species. Among the 84 morphospecies, molecular species identification of 60 species (71.4%) was consistent with their morphological identifications. Six cryptic and/or pseudocryptic species with large genetic divergence (>5%) were confirmed by their sympatric or allopatric distributions. However, 18 species, including a subspecies, had ambiguous genetic distances and shared overlapping intra- and interspecific genetic distances (range: 2.12%–3.67%) suggesting incomplete lineage sorting, introgression of mitochondrial genome, or affection by endosymbionts, such as Wolbachia infection, between species and simple genetic variation within species. In this study, we propose a conservative threshold of 3.6% for convenient molecular operational taxonomic unit (MOTU) identification in the subfamily Denticollinae based on the results of pairwise genetic distances analyses using neighbor-joining, mothur, Automatic Barcode Gap Discovery analysis, and tree-based species delimitation by Poisson Tree Processes analysis. Using the 3.6% threshold, we identified 87 MOTUs and found 8 MOTUs in the interval between 2.5% to 3.5%. Evaluation of MOTUs identified in this range requires integrative species delimitation, including review of morphological and ecological differences as well as sensitive genetic markers. From this study, we confirmed that COI sequence is useful for reassessing species diversity for polymorphic and polytypic species occurring in sympatric and allopatric distributions, and for a single species having an extensively large habitat.
Highlights
Coleoptera is the most diverse order in the world with nearly 400,000 named species [1]
We examined two effective approaches to grouping hypothetical species, such as Automatic Barcode Gap Discovery (ABGD) based on pairwise genetic distances [61] and the Poisson Tree Processes (PTP) model based on the rooted phylogenetic trees [62]
A total of 421 c oxidase subunit I (COI) sequences representing 84 morphospecies belonging to 36 genera of 3 tribes, Hypnoidini, Denticollini, and Ctenicerini, were successfully generated to test the utility of DNA barcoding for species identification in the subfamily Denticollinae (S2 Table)
Summary
Coleoptera is the most diverse order in the world with nearly 400,000 named species [1]. Many cryptic species have been reported in this order Recognition of cryptic species diversity is essential to establishing conservation policies and pest control strategies for focal species. Extremely similar or indistinguishable morphological features represented in many Coleoptera species have at times impaired morphological identification [10]. DNA barcoding has recently become entrenched as the standard method for molecular species identification [11], achieving successful identification rates of up to 97% in various animal taxa [12,13,14,15,16]. Analysis of DNA sequences is currently regarded as essential for the detection of hidden species [17,18]
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