Reassessment of the Species in the Euwallacea Fornicatus (Coleoptera: Curculionidae: Scolytinae) Complex after the Rediscovery of the “Lost” Type Specimen

Abstract

Ambrosia beetles of the Euwallacea fornicatus (Eichhoff, 1868) species complex are emerging tree pests, responsible for significant damage to orchards and ecosystems around the world. The species complex comprises seven described species, all of which are nearly identical. Given that the morphology-defined species boundaries have been ambiguous, historically, there has been much disagreement on species validity, which was compounded by the presumed loss of the type series of E. fornicatus. The species complex was recently reviewed using morphometrics to associate the type specimens to the clades delineated with molecular data under the assumption of the lost type series. We rediscovered a syntype of Xyleborus fornicatus, and reevaluated the species in the complex using morphometrics. We propose the following taxonomic changes to the species complex: Euwallacea fornicatus (=E. tapatapaoensis (Schedl, 1951); = E. whitfordiodendrus (Schedl, 1942)) syn. res.); E. fornicatior (Eggers, 1923) (=E. schultzei (Schedl, 1951) syn. nov.); E. kuroshio (Gomez and Hulcr, 2018) and E. perbrevis (Schedl, 1951) stat. res. These taxonomic changes shift the species name associated with the widely used common names for two taxa, namely: Euwallacea fornicatus should be used for the “Polyphagous Shot Hole Borer”, and E. perbrevis for the “Tea Shot Hole Borer clade a”. A lectotype is designated for X. fornicatus in order to stabilize the use of the name.

The Essential Role of Taxonomic Expertise in the Creation of DNA Databases for the Identification and Delimitation of Southeast Asian Ambrosia Beetle Species (Curculionidae: Scolytinae: Xyleborini)

“…The E. fornicatus species complex has recently received much taxonomic attention given their pest status and that different lineages impart various levels of economic damage. Although qualitative diagnostic characters were not observed, consistent quantitative characters, and morphometric analysis were congruent with lineages that demonstrated >10% COI difference compared to each other (Stouthamer et al, 2017;Gomez et al, 2018;Smith et al, 2019). In addition, potential pre-and post-mating reproductive barriers and fidelity with different symbiotic fungal strains support the validity of the recognized species (Kasson et al, 2013;Cooperband et al, 2015Cooperband et al, , 2017.…”

“…It is estimated that only 75% of the Southeast Asian and 25% of the South American faunas have been described so far (Wood and Bright, 1992;Hulcr et al, 2015;Smith et al, 2017). Even with taxonomic tools, the small and subtle morphological differences that define many xyleborine species make it difficult for non-experts to accurately identify species (Cognato et al, 2015;Gomez et al, 2018;Hoebeke et al, 2018;Smith et al, 2019). Identification of immature stages to species or genus presents the greatest challenge even for experts.…”

Peer Review #2 of "One becomes two: second species of the Euwallacea fornicatus (Coleoptera: Curculionidae: Scolytinae) species complex is established on two Hawaiian Islands (v0.1)"

“…The respective sequences were retrieved from GenBank, combined with the Hawaiian sequences and collapsed into haplotypes using DnaSP version 5.10.01 (Librado & Rozas, 2009). The H8 haplotype of E. perbrevis (Stouthamer et al, 2017;Smith et al, 2019) was added to root the analysis, and the entire dataset was trimmed to 567bp. Genealogical relationships among the haplotypes were investigated by conducting a maximum likelihood (ML) analysis in RAxML version 8.2.10 (Stamatakis, 2014) using the RAXMLGUI v. 2.0.0.-beta6 (Edler et al, 2019).…”

“…Thus, TSHB was thought to be the only species of the E. fornicatus species complex to have invaded Hawaiʻi (Stouthamer et al, 2017). Recent attempts to associate existing junior synonyms with these species (Gomez et al 2018;Smith et al, 2019) have resulted in the current association of the scientific name E. perbrevis with this species (Smith et al, 2019). Following the publication of the Stouthamer et al (2017) study, we discovered that in September 2016, a conflicting COI sequence was belatedly deposited in GenBank, which originated from two beetles collected from macadamia trees on the Big Island.…”

“…Following the publication of the Stouthamer et al (2017) study, we discovered that in September 2016, a conflicting COI sequence was belatedly deposited in GenBank, which originated from two beetles collected from macadamia trees on the Big Island. The COI sequence identified these beetles as E. fornicatus (Smith et al, 2019) (or PSHB as we choose to refer to it), and they were collected in 2007 by Australian scientists studying the pests attacking macadamia trees in Hawaiʻi (Mitchell & Maddox, 2010). For simplicity, hereafter we refer to E. perbrevis and E. fornicatus as TSHB and PSHB, respectively.…”