Wireworm (Coleoptera: Elateridae) genomic analysis reveals putative cryptic species, population structure, and adaptation to pest control

Abstract

The larvae of click beetles (Coleoptera: Elateridae), known as “wireworms,” are agricultural pests that pose a substantial economic threat worldwide. We produced one of the first wireworm genome assemblies (Limonius californicus), and investigated population structure and phylogenetic relationships of three species (L. californicus, L. infuscatus, L. canus) across the northwest US and southwest Canada using genome-wide markers (RADseq) and genome skimming. We found two species (L. californicus and L. infuscatus) are comprised of multiple genetically distinct groups that diverged in the Pleistocene but have no known distinguishing morphological characters, and therefore could be considered cryptic species complexes. We also found within-species population structure across relatively short geographic distances. Genome scans for selection provided preliminary evidence for signatures of adaptation associated with different pesticide treatments in an agricultural field trial for L. canus. We demonstrate that genomic tools can be a strong asset in developing effective wireworm control strategies.

Genetic structure and population demographics of Hypnoidus bicolor (Coleoptera: Elateridae) in the Canadian Prairies

“…Despite appearing morphologically indistinguishable from one another and often present in the same populations across our sampling region, the minimum sequence divergence among haplotypes of 4.7% was surprisingly high for an intraspecific comparison. Indeed, COX1 divergence within the same animal species is generally <1%, and <2% divergence is typically found among conspecific invertebrate populations 9,45 . Benefer and co‐authors also detected two diverse groups among 41 H. bicolor samples collected in Canada using mtDNA 16S rRNA markers 14 .…”

“…Although we do not have sufficient evidence to characterize the genetic clades as different species, it is possible that they will respond differently to control measures. Indeed, the effectiveness of management approaches for wireworms can differ significantly between closely related species 9 . Wireworm larval stages and species are often difficult to discern due to their cryptic nature and lack of distinguishing characteristics; thus, effective IPM strategies rely on determining the species and genetic variants present in a given population or region.…”

“…However, current IPM strategies are impeded by large gaps in knowledge related to species diversity across regions, subterranean ecology, duration and cryptic behavior during the larval stages, as well as vertical movement in the soil profile and other interspecific variations (e.g., seasonal periods of inactivity) 7,8 . Furthermore, morphological identification of wireworms—a crucial step in management—is difficult due to few distinguishable characters between species and a limited number of experts that can discern between species 9 . Population genetic tools have the potential to provide some of this missing information and assist in the development of effective IPM approaches for wireworms.…”

“…Damage is caused when larvae burrow into germinating seeds and seedlings, or feed on the cotyledons, young roots, stems, tubers and other parts of the plant found in or near the soil 1,10 . Wireworms differ from other agricultural pest species in the time spent in their larval stages, which ranges between 1 and 11 years depending on the species and environmental conditions 9–11 . Nine wireworm pest species have been found in the Canadian Prairies, with Hypnoidus bicolor (Eschscholtz, 1829) frequently occurring on agricultural land 12 .…”

Alternative Strategies for Controlling Wireworms in Field Crops: A Review

“…Both the molecular method (PCR) and the morphological methods have their difficulties, but both produce reliable results for most individuals [13,39,40,72,191]. Additionally, recent molecular research suggested a possible occurrence of cryptic species in some North American wireworms [72,192], which may also affect the efficacy of a biological product. Furthermore, the activity pattern and damage potential of different wireworms in a crop may differ, which could affect the risk a certain species poses for a certain crop [35,153].…”