Bactrocera tryoni species complex

Taxonomy

Based on morphology alone, four species had been included in the B. tryoni species complex: B. tryoni, B. neohumeralis, B. melas, and B. aquilonis. Since the molecular phylogenetics study of Starkie et al. 2022aStarkie et al. 2022a:
Starkie ML, Cameron SL, Krosch MN, Phillips MJ, Royer JE, Schutze MK, Strutt F, Sweet AD, Zalucki MP, Clarke AR, 2022. A comprehensive phylogeny helps clarify the evolutionary history of host breadth and lure response in the Australian Dacini fruit flies (Diptera: Tephritidae). Molecular Phylogenetics and Evolution 172: 107481. https://doi.org/10.1016/j.ympev.2022.107481 , four more species are included: B. erubescentis, B. mutabilis, B. curvipennis and B. ustulata.

Valid name: Bactrocera (Bactrocera) tryoni (Froggatt, 1897)
Preferred common name: Queensland fruit fly

Valid name: Bactrocera (Bactrocera) neohumeralis (Hardy, 1951)
Valid name: Bactrocera (Bactrocera) melas (Perkins & May, 1949)
Valid name: Bactrocera (Bactrocera) aquilonis (May, 1965)
Valid name: Bactrocera (Bactrocera) erubescentis (Drew & Hancock, 1981)
Valid name: Bactrocera (Bactrocera) mutabilis (May, 1952)
Valid name: Bactrocera (Bactrocera) curvipennis (Froggatt, 1909)
Valid name: Bactrocera (Bactrocera) ustulata Drew, 1989Drew, 1989:
Drew RAI, 1989. The tropical fruit flies (Diptera: Tephritidae: Dacinae) of the Australasian and Oceanian regions. Memoirs of the Queensland Museum 1: 1–521.

There is a long-standing scientific dispute on whether B. aquilonis and B. tryoni are synonymous (Cameron et al. 2010Cameron et al. 2010:
Cameron EC, Sved JA, Gilchrist AS, 2010. Pest fruit fly (Diptera: Tephritidae) in northwestern Australia: one species or two? Bulletin of Entomological Research 100: 197–206. https://doi.org/10.1017/S0007485309990150). Bactrocera neohumeralis found in New Guinea may be a separate species from B. neohumeralis found in Australia; they feed on different hosts (Leblanc. pers. comm.).

Morphology-based identification

Bactrocera tryoni and B. aquilonis are only differentiated by their geographic origin, there are no consistent morphological characters to distinguish them. Other species in the complex can be identified based on morphological characters.

Spot characters to distinguish B. tryoni from B. dorsalis are an overall more reddish appearance of B. tryoni and tapering yellow lateral vittae on the scutum, which are parallel in B. dorsalis.

Molecular identification

The presence of nuclear pseudogenes hampers COI amplification and sequencing of B. tryoni (Blacket et al. 2012Blacket et al. 2012:
Blacket MJ, Semeraro L, Malipatil MB, 2012. Barcoding Queensland fruit flies (Bactrocera tryoni): Impediments and improvements. Molecular Ecology Resources 12: 428–436. https://doi.org/10.1111/j.1755-0998.2012.03124.x), and COI sequence data cannot distinguish any of the species within the complex (Starkie et al. 2022aStarkie et al. 2022a:
Starkie ML, Cameron SL, Krosch MN, Phillips MJ, Royer JE, Schutze MK, Strutt F, Sweet AD, Zalucki MP, Clarke AR, 2022. A comprehensive phylogeny helps clarify the evolutionary history of host breadth and lure response in the Australian Dacini fruit flies (Diptera: Tephritidae). Molecular Phylogenetics and Evolution 172: 107481. https://doi.org/10.1016/j.ympev.2022.107481 ), but they can be used to identify a specimen as belonging to the complex as a whole.

The PAN gene region has two adjacent SNPs that can distinguish B. tryoni from B. neohumeralis (Starkie et al. 2023Starkie et al. 2023:
Starkie ML, Fowler EV, Piper AM, Zhu X, Wyatt P, Gopurenko D, Krosch MN, Strutt F, Armstrong KF, Patrick H, Schutze MK, Blacket MJ, 2023. A novel diagnostic gene region for distinguishing between two pest fruit flies: Bactrocera tryoni (Froggatt) and Bactrocera neohumeralis (Hardy) (Diptera: Tephritidae). Insect Science: 1744-7917.13299. https://doi.org/10.1111/1744-7917.13299).

Distribution

The B. tryoni species complex is restricted to the Australasian region. Bactrocera tryoni is only known from Australia, Queensland and along the East Coast, B. aquilonis is only known from the Northern Territory. Bactrocera erubescentis and B. neohumeralis are found in New Guinea and Queensland (but see taxonomy comment above). Bactrocera melas and B. mutabilis are found in Queensland, B. curvipennis in New Caledonia, and B. ustulata in New Guinea.

Further information

B. tryoni and B. neohumeralis are listed as "category A" pests in Vargas et al. 2015Vargas et al. 2015:
Vargas RI, Pinero JC, Leblanc L, 2015. An overview of pest species of Bactrocera fruit flies (Diptera: Tephritidae) and the integration of biopesticides with other biological approaches for their management with a focus on the pacific region. Insects 6: 297–318. https://doi.org/10.3390/insects6020297. A category A pest is defined as "widespread invasive polyphagous generalists or highly destructive specialists that have become established outside of their native range".

Bactrocera aquilonis and B. curvipennis are listed as "category B" pests in Vargas et al. 2015Vargas et al. 2015:
Vargas RI, Pinero JC, Leblanc L, 2015. An overview of pest species of Bactrocera fruit flies (Diptera: Tephritidae) and the integration of biopesticides with other biological approaches for their management with a focus on the pacific region. Insects 6: 297–318. https://doi.org/10.3390/insects6020297. A category B pest is there defined as "polyphagous fruit pests or destructive specialists more restricted in distribution, but at elevated risk of spreading to new locations".

Bactrocera melas is listed as a "category C" polyphagous pest in Australia in Vargas et al. 2015Vargas et al. 2015:
Vargas RI, Pinero JC, Leblanc L, 2015. An overview of pest species of Bactrocera fruit flies (Diptera: Tephritidae) and the integration of biopesticides with other biological approaches for their management with a focus on the pacific region. Insects 6: 297–318. https://doi.org/10.3390/insects6020297. A category C pest is there defined as "relatively minor oligophagous or specialist fruit or cucurbit pests".

Bactrocera mutabilis is listed as a "category D" pest of Australia in Vargas et al. 2015Vargas et al. 2015:
Vargas RI, Pinero JC, Leblanc L, 2015. An overview of pest species of Bactrocera fruit flies (Diptera: Tephritidae) and the integration of biopesticides with other biological approaches for their management with a focus on the pacific region. Insects 6: 297–318. https://doi.org/10.3390/insects6020297. A category D pest is there defined as "species that have been occasionally bred from commercial/edible fruit or cucurbits".