Newly Emerging Pest in China, Rhynchaenusmaculosus (Coleoptera: Curculionidae): Morphology and Molecular Identification with DNA Barcoding

Abstract

The oak flea weevil, Rhynchaenus maculosus Yang et Zhang 1991, is a newly emerging pest that severely damages oak (genus Quercus) in China. The first R. maculosus outbreak occurred in 2020 and caused spectacular damage to all oak forests in Jilin province, northeast China. The lack of key morphological characters complicates the identification of this native pest, especially in larva and pupa stages. This is problematic because quick and accurate species identification is crucial for early monitoring and intervention during outbreaks. Here, we provided the first detailed morphological description of R. maculosus at four life stages. Additionally, we used DNA barcodes from larva and pupa specimens collected from three remote locations for molecular identification. The average pairwise divergence of all sequences in this study was 0.51%, well below the 2% to 3% (K-2-parameter) threshold set for one species. All sample sequences matched the R. maculosus morphospecies (KX657706.1 and KX657707.1), with 99.23% to 100% (sequence identity, E value: 0.00) matching success. The tree based on barcodes placed the specimens into the Rhynchaenus group, and the phylogenetic relationship between 62 sequences (30 samples and 32 from GeneBank) had high congruence with the morphospecies taxa. The traditional DNA barcodes were successfully transformed into quick response codes with larger coding capacity for information storage. The results showed that DNA barcoding is reliable for R. maculosus identification. The integration of molecular and morphology-based methods contributes to accurate species identification of this newly emerging oak pest.

Biology of Rhynchaenus maculosus provides insights and implications for integrated management of this emerging pest

“…Distribution of an insect pest is one of the population properties, which is of great significance either in theoretical ecology as well as in pest monitoring and control 19 , especially for a newly-emerging pest. Our studies showed that R. maculosus , a newly-emerging insect pest in recent years 2 , is distributed locally in Northeast China, including the Liaoning, Jilin, and Heilongjiang provinces. Some leaf-mining pests in the weevil family have become invasive pests, causing economic and ecological impacts to the newly introduced areas 20 .…”

“…Three oak forests over 100 km apart in each province were selected to collect the insect pests. The collection of adult samples was performed using sticky traps around the trunk combined with hand-collection from mid-April to early May each year 2 . The insect samples were taken into laboratory for species identification carried out by both morphology and molecular method.…”

“…At each sampling point, two oak trees with a distance of three meters were selected. For each oak tree, a rectangular sticky trap (20 cm × 25 cm) around the trunk at 10 cm high above the ground was used for capturing the active overwintering adults 2 . The number of active adults stuck by the trap was surveyed at the same time each day from mid-April to mid-May in Liaoning and Jilin, from late-April to late-May in Heilongjiang.…”

“…The oak flea weevil Rhynchaenus maculosus (Coleoptera, Curculionidae, Rhynchaeninae), is an emerging pest of oak in China 1 , 2 . It was first discovered and described in 1991 as a new insect species collected in 1987 from Greater Xing'an Mountains, Heilongjiang province 3 .…”

Delimiting species, revealing cryptic diversity, and population divergence in Qinghai‐Tibet Plateau weevils through DNA barcoding

“…DNA barcoding, a method for species identification based on standard gene markers, for example, the mitochondrial cytochrome oxidase subunit I (COI) gene for animals, has become a reliable basis for assembling reference sequence libraries of known species and discovering new species in many taxonomic groups (Hebert et al., 2003 ; Hebert et al., 2004 ). The efficacy of this approach has been successfully demonstrated across various taxa of Coleoptera, including Curculionidae (Astrin et al., 2012 ; Ma et al., 2022 ; Yang et al., 2021 ), Coccinellidae (Huang et al., 2020 ), and Tenebrionidae (Li et al., 2020 ). Previous studies have also shown the effectiveness of DNA barcoding in species identification and diagnosis within the Curculionoidea (Germann et al., 2017 ; Ma et al., 2022 ).…”