One becomes two: second species of the Euwallacea fornicatus (Coleoptera: Curculionidae: Scolytinae) species complex is established on two Hawaiian Islands

Abstract

The cryptic species that make up the Euwallacea fornicatus species complex can be readily distinguished via their DNA sequences. Until recently, it was believed that the Hawaiian Islands had been invaded by only one of these cryptic species, E. perbrevis (tea shot hole borer; TSHB). However, following the 2016 deposition of a DNA sequence in the public repository GenBank, it became evident that another species, E. fornicatus (polyphagous shot hole borer; PSHB), had been detected in macadamia orchards on Hawaiʻi Island (the Big Island). We surveyed the two most-populous islands of Hawaiʻi, Big Island and Oʻahu, and herein confirm that populations of TSHB and PSHB are established on both. Beetles were collected using a variety of techniques in macadamia orchards and natural areas. Individual specimens were identified to species using a high-resolution melt assay, described herein and validated by subsequent sequencing of specimens. It remains unclear how long each species has been present in the state, and while neither is currently recognized as causing serious economic or ecological damage in Hawaiʻi, the similarity of the newly-confirmed PSHB population to other damaging invasive PSHB populations around the world is discussed. Although the invasive PSHB populations in Hawaiʻi and California likely have different geographic origins within the beetle’s native range, they share identical Fusarium and Graphium fungal symbionts, neither of which have been isolated from PSHB in that native range.

Chromosome structural rearrangements in invasive haplodiploid ambrosia beetles revealed by the genomes ofEuwallacea fornicatusandEuwallacea similis(Coleoptera, Curculionidae, Scolytinae)

“…It has been recorded to attack over 680 tree species across several plant families (Department of Primary Industries and Regional Development, Government of Western Australia, 2024; Gomez et al, 2019; Mendel et al, 2021) and is able to successfully reproduce in 168 species (Department of Primary Industries and Regional Development, Government of Western Australia, 2024 (and references therein), Mendel et al, 2021). Euwallacea fornicatus is widely distributed and has been introduced to California (Eskalen et al, 2012, 2013), Hawaii (Rugman-Jones et al, 2020), South Africa (Paap et al, 2018), Israel (Mendel et al, 2012), Europe (Schuler et al, 2023) and, recently, in the city of Perth, Western Australia (WA) where it is currently subject to an eradication campaign (Department of Agriculture, Fisheries and Forestry, 2024). This ambrosia beetle species is associated with several pathogenic Fusarium fungi, including F. euwallaceae Freeman et al .…”

The worldwide invasion history of a pest ambrosia beetle inferred using population genomics

“…For example, the Euwallacea fornicatus species complex was considered a single species when it was first described outside its native area, but is now considered to comprise seven species with overlapping morphologies (Smith et al, 2019). Studying its population genetic structure in Hawaii revealed the co-occurrence of two species of the complex (Rugman- Jones et al, 2020). Such findings can affect detection protocols and management decisions, for example, by helping find suitable natural enemies for biological control (Stouthamer et al, 2017).…”

Rapid and cost‐effective detection of Fusarium euwallaceae from woody tissues

“…The polyphagous shot hole borer (PSHB) Euwallacea fornicatus (Coleoptera: Curculionidae: Scolytinae) is a woodboring ambrosia beetle native to Asia, but it has now successfully established in Australia, South Africa, and Hawaii and California in the United States (Eskalen et al, 2012; IPPC, 2021; Mendel et al, 2012; Paap et al, 2018; Rugman‐Jones et al, 2020). One reason ascribed to its invasive success is its wide host range.…”