The six-spotted spider mite, Eotetranychus sexmaculatus (Riley) (Tetranychidae): morphological and molecular analyses
Citation
Beard JJ, Beaulieu F, Knee W, Gotoh T. 2022. The six-spotted spider mite, Eotetranychus sexmaculatus (Riley) (Tetranychidae): morphological and molecular analyses. In: Zhang, Z.-Q., Fan, Q.-H., Heath, A.C.G. & Minor, M.A. (Eds) Acarological Frontiers: Proceedings of the XVI International Congress of Acarology (1–5 Dec. 2022, Auckland, New Zealand). Magnolia Press, Auckland, 328 pp. (Zoosymposia 22: 192; conference abstract)
Résumé en langage clair
The abstract of an oral presentation was published in the proceedings of the 16th International Congress of Acarology that occurred in Auckland, New Zealand (see below a copy of the abstract). This collaborative research is dealing wit the identity and distribution of the six-spotted spider mite (Eotetranychus sexmaculatus), a pest of various crops, including avocado, citrus or vineyards, in North America and overseas.
Résumé
A spider mite species initially identified as the six-spotted spider mite, Eotetranychus sexmaculatus (Riley), was recorded defoliating avocado trees, Persea americana Mill. (Lauraceae), in the southwestern parts of Western Australia. However, due to morphological inconsistencies in the descriptions of E. sexmaculatus, it has recently been suggested that these Australian specimens actually represented the native species E. queenslandicus Manson and that E. sexmaculatus was in fact not present in Australia (Seeman et al. 2017). This conflict resulted in an investigation into the taxonomic history of E. sexmaculatus and its possible synonyms, including E. asiaticus Ehara, a species that is so morphologically close to E. sexmaculatus that it was in fact described (Ehara 1966) from material that was originally identified as the first record of E. sexmaculatus in Japan (Ehara 1956). Both Seeman et al. (2017) and Gotoh & Arabuli (2019) have previously noted that both these taxa, and E. queenslandicus, closely resemble each other and are difficult to separate. Consequently, detailed morphological and molecular analyses were undertaken to test their conspecificity by comparing type specimens of E. queenslandicus and E. asiaticus, specimens of E. sexmaculatus from near the type location (Florida, USA) on the type host (Citrus), as well as non-type specimens from Australia (putatively E. queenslandicus), New Zealand, Japan (putatively E. asiaticus), USA (Florida, Hawaii, California) and Taiwan. Selected non-types were further compared using the cytochrome c oxidase subunit I (COI) gene of mitochondrial DNA and the internal transcribed spacer 2 (ITS2) of nuclear DNA. Based on the results of morphological and molecular analyses, we discuss the validity of these three species.