The genus Glochidion in Phyllanthaceae comprises 170 accepted species, and its members are mostly distributed in the Indo-Malay and Australasia regions with one exception in the Palearctic region (Royal Botanic Gardens, Kew, n.d.). The one species in the Palearctic region is Glochidion chodoense C.S. Lee and H.T. Im, 1994 that was described from Chodo (=Jodo) Archipelago in South Korea. The species is currently known to occur only in Chodo and Jindo Islands (Lee and Im, 1994;KNA, 2024). The plant species is a Korean endemic species and was listed as ‘Critically Endangered’ by IUCN category (Kim et al., 2016).

Monecious tree genus Glochidion is known to have highly versified species-specific pollination mutualism with a moth genus Epicephala (Gracillariidae) (e.g. Kato et al., 2003;Kawakita and Kato, 2009). According to Kato et al (2003), female moths are active at night, collecting pollen on their proboscis from male flowers and deposit them onto the stigmas of female flowers. After the pollen deposition, the gracillariid moth subsequently oviposit eggs through the ovary wall. A hatched larva starts consuming a few immature seeds, usually two seeds in G. acuminatum.

Another study surveyed a phytophagous insect community that fed internally on Glochidion trees in south-eastern Polynesia and compared the result with information from continental faunas (Hembry et al., 2013). The result showed that most of them were lepidopterans that could be categorized largely into three as follows: seed-feeding moths (Gracillariidae, including Epicephala, and Tortricidae), leaf-mining moths (Gracillariidae), and leaf-rolling moths (Tortricidae).

In South Korea, a study on such interactions between G. chodoense and phytophagous insects has never been made until recent years. Back in 2020, Jindo county office established an in-situ conservation site of the plant in consideration of its value as an endemic species. In the effort for the species conservation, the county office and National Institute of Forest Science teamed up and brought up a plan to use the plant as street ornamental trees and tried to collect the seeds for a nursery. However, the seeds during winter season (after November) were almost completely consumed by various unidentified insect pests. Several field surveys were made to identify those insect pests, and an unrecorded curculionid was found being active at night and mostly near female flowers. Also, some unknown coleopteran larvae were found inside the fruits.

The current study is to make a report on a newly recognized curculionid that belongs to the tribe Ochyromerini in the subfamily Curculioninae and feeds on immature seeds of G. chodoense. We provide the brief diagnosis on the species and the photographic images of host plant and adult of this species and related species. Also sequence of Mitochondrial DNA barcode data are provided with NCBI accession numbers.

Materials and Methods

All specimens were collected from a conservation site of G. chodoense located in Jindo Island, Jindo-gun, Jeollanam-do, South Korea (Fig. 1A–C). The adult specimens were directly collected from the flowers and branches of the host plant at night (Fig. 1D), and larval samples were obtained by dissecting 30 immature fruits (Fig. 2).

The materials for this study are deposited in the collection of Research Institute of Forest Insect Diversity (RIFID, Namyangju, Korea) and Korea National Arboretum (KNA, Pocheon, Korea). The important morphological characters were examined using a stereoscopic microscope (S8Apo, Leica, Heerbrugg, Switzerland). Photographs of adult were taken with Canon 5D digital camera and Canon Macro Photos Lens MP-E 65 (Canon, Tokyo, Japan). The ovary and larvae images were captured using Dhyana 400dc camera (Tucsen Photonics, Fuzhou, China) mounted on a Leica M205C compound microscope (Leica Microsystems, Wetzlar, HESSE, Germany). Multiple images were stacked using Helicon Focus version 8.2.0.

The genomic DNA extraction was performed using the DNeasy Blood & Tissue Kit (Qiagen, Hilden, Germany) according to the manufacturer protocol. Total of four specimens, comprising one adult and three larvae, were sequenced for a 658 bp fragment of the mitochondrial cytochrome c oxidase I (COI) gene. The primer pair LCO-1490 (5'-GGTCAACAAATCATAAAGATATTGG- 3') and HCO-2198 (5'-TAAACTTCAGGGTGACCAAAAAATCA- 3') was used to amplify the DNA barcode (Folmer et al., 1994). The PCR amplification was performed for (Platinum Taq, Invitrogen, Carlsbad City, CA, USA) and amplicons were purified using the QIAquick^® PCR Purification Kit (QIAGEN, Inc., Hilden, Germany). The final PCR products were sequenced at Macrogen (Seoul, Korea). The resulting sequences were edited and aligned using the ClustalW method, and genetic divergence was then analyzed in MEGA based on pairwise distance estimation under the Kimura 2-parameter model.

Taxonomic Accounts

Order Coleoptera 딱정벌레목

Superfamily Curculionoidea Latreille, 1802 바구미상과

Family Curculionidae Latreille, 1802 바구미과

Subfamily Curculioninae Latreille, 1802 밤바구미아과

Tribe Ochyromerini Voss, 1935

Genus NesendaeusMarshall, 1931 조도만두바구미속(신칭)

NesendaeusMarshall, 1931: 270 (Type species Nesendaeus setolineatusMarshall, 1931)

Distribution. Korea (new record), China, Samoa.

Nesendaeus monochrousVoss, 1953 담갈색조도만두바구 미(신칭)(Figs. 1E–G, 2D–F)

Nesendaeus monochrousVoss, 1953: 53 (Type locality: Fukien-China).

Diagnosis. Body elongated oval, slightly flattened ventrally, 3.2–3.4 × as long as wide, 3.2–3.5 mm long (including rostrum), with colour uniformly reddish-brown to dark yellowishbrown; legs, antennae, and rostrum concolorous or slightly lighter; eyes black (Fig. 1E–G). Dorsal surface moderately shining, covered with dense, recumbent, fine setae and scattered minute scale-like setae. Head with rostrum slender, parallelsided, approximately 1.2 × as long as pronotum, weakly curved in lateral view, surface roughly and densely punctate with longitudinally rugate sculpture. Frons narrow, width across eyes as wide as rostral width at base. Eyes large, lateral, oval, moderately protruding, coarsely faceted. Antennal scape elongated, reaching to anterior margin of eye, funicle 7-segmented, club compact, oval, approximately as long as last four funicular segments combined. Pronotum slightly wider than long (width/ length ratio 1.05–1.08), widest at basal one third, sides weakly arcuate, anterior margin almost straight, disc weakly convex. Surface densely punctate with big and shallow punctures, punctures separated by less than their own diameter. Vestiture of short, fine, recumbent setae evenly distributed but almost invisible. Elytra elongate, 1.7–1.8 × as long as wide, 2.4–2.5 × as long as pronotum, sides subparallel in basal two-thirds, broadly rounded apically. Striae distinct, consisting of large, deep, round punctures, each separated by less than one puncture diameter. Interstriae weakly convex, slightly narrower than striae, with minute granules and fine, recumbent setae. Humeral angles weakly edged. Elytra apex bisinuately round without denticles or spines. Legs moderately robust. Femora clavate, each with a distinct acute tooth on inner margin at approximately two-thirds from base, femoral surface finely punctate, with short recumbent setae. Tibiae weakly arched, subequal in length to femora, with apical inner margins bearing a small uncus, outer margin unarmed. Tarsi with first segment elongate, second shorter, third distinctly bilobed, fourth elongate; claws simple, free, each with a small, triangular inner tooth near base.

Distribution. Korea (new record), China.

Specimens examined. 1♂2♀. Namdong-ri, Imhoe-myeon, Jindo-gun, Jeollanam-do, 31.vii.2023, Gyu Young Han., A Young Kim leg.

DNA accession number. Sequences were uploaded to NCBI (Accession numbers: PX258066, PX258067, PX258068, and PX258069).

Biology. Based on periodic field survey results, adults of N. monochrous are active on the branches and female flowers of G. chodoense from June to August (Fig. 1D). The larvae were found to feed on the immature seeds of G. chodoense fruits, leaving frass near the feeding wounds, and up to three larvae were found within a single fruit (Fig. 2). Their occurrence appears to coincide with the early half flowering period of G. chodoense, which is from May to November, as they were not observed from September to November. In particular, further studies are needed to clarify aspects of their life history, including overwintering stages and the number of generations per year.

Genetic divergence. The pairwise distance estimation using COI sequences (PX258066–PX258069) of one adult and three larvae, revealed conspecificity between adults and larvae with negligible genetic divergence (0.0–0.6%) (Table 1).

Discussion

This species appears morphologically similar to Heterochyromera imerodeusKojima and Morimoto, 1996 but easily distinguishable from it by the relatively longer elytra and bisinuate apical margin of elytra (Fig. 1E–H). H. imerodeus Kojima and Morimoto in Japan can be found from Eurya emarginata (Thunb.) Makino and Glochidion obovatum Siebold and Zucc. (Kojima and Morimoto, 1996). The DNA barcode sequence of H. imerodeus is currently unavailable in NCBI, and thus the degree of its phylogenetic affinity to N. monochrous remains uncertain. The morphological resemblance and similarity in host associations between Nesendaeus and Heterochyromera may indicate a closer relationship than previously recognized. To evaluate whether these similarities reflect an actual phylogenetic affinity, additional molecular data, including that of H. imerodeus, will be required.