One and the same: integrative taxonomic evidence that Bactrocera invadens (Diptera: Tephritidae) is the same species as the Oriental fruit fly Bactrocera dorsalis

Abstract

The invasive fruit fly Bactrocera invadens Drew, Tsuruta & White, and the Oriental fruit fly Bactrocera dorsalis (Hendel) are highly destructive horticultural pests of global significance. Bactrocera invadens originates from the Indian subcontinent and has recently invaded all of sub-Saharan Africa, while B. dorsalis principally occurs from the Indian subcontinent towards southern China and South-east Asia. High morphological and genetic similarity has cast doubt over whether B. invadens is a distinct species from B. dorsalis. Addressing this issue within an integrative taxonomic framework, we sampled from across the geographic distribution of both taxa and: (i) analysed morphological variation, including those characters considered diagnostic (scutum colour, length of aedeagus, width of postsutural lateral vittae, wing size, and wing shape); (ii) sequenced four loci (ITS1, ITS2, cox1 and nad4) for phylogenetic inference; and (iii) generated a cox1 haplotype network to examine population structure. Molecular analyses included the closely related species, Bactrocera kandiensis Drew & Hancock. Scutum colour varies from red-brown to fully black for individuals from Africa and the Indian subcontinent. All individuals east of the Indian subcontinent are black except for a few red-brown individuals from China. The postsutural lateral vittae width of B. invadens is narrower than B. dorsalis from eastern Asia, but the variation is clinal, with subcontinent B. dorsalis populations intermediate in size. Aedeagus length, wing shape and wing size cannot discriminate between the two taxa. Phylogenetic analyses failed to resolve B. invadens from B. dorsalis, but did resolve B. kandiensis. Bactrocera dorsalis and B. invadens shared cox1 haplotypes, yet the haplotype network pattern does not reflect current taxonomy or patterns in thoracic colour. Some individuals of B. dorsalis/B. invadens possessed haplotypes more closely related to B. kandiensis than to conspecifics, suggestive of mitochondrial introgression between these species. The combined evidence fails to support the delimitation of B. dorsalis and B. invadens as separate biological species. Consequently, existing biological data for B. dorsalis may be applied to the invasive population in Africa. Our recommendation, in line with other recent publications, is that B. invadens be synonymized with B. dorsalis.

A global checklist of the 932 fruit fly species in the tribe Dacini (Diptera, Tephritidae)

“…The largest and most intesively studied is the Bactrocera dorsalis complex with 88 species; the group that, incidentally, also holds the largest number of pest species. This complex, like most others, is not monophyletic (Leblanc et al 2015b, Virgilio et al 2015, San Jose et al 2018 in press) and there has been synonymy of several significant pest species, such as B. papayae Drew & Hancock, 1994, and B. invadens Drew, Tsuruta & White, 2005 with B. dorsalis (San Jose et al 2013, Schutze et al 2015a, 2015b). To facilitate communication and progress of our understanding of the group, a reliable taxonomic starting point is badly needed and will enable further studies into the taxonomy and systematics of the tribe.…”

“…The source data is, for a large part, comprised of regional treatments (Drew 1989, Hancock and Drew 2006, White 2006, Drew and Romig 2013), with additions and revisions from more recent studies (Drew et al 2011, Yu et al 2012, Hancock 2015, Hancock and Drew 2015, Hendrichs et al 2015, Schutze et al 2015b, David et al 2016, 2017, Drew and Hancock 2016, Freidberg et al 2017, Han et al 2017). Species included in the list are ordered alphabetically by genus.…”

Impact of Oriental Fruit Fly Postharvest Treatments on Avocado

“…The oriental fruit fly, Bactrocera dorsalis (Hendel), is of particular concern due to its destructive impact on fruit and vegetable production [3]. The damage occurs through oviposition punctures and subsequent larval development in fruit [4].…”

“…Native to tropical Asia, B. dorsalis is also established over much of sub-Saharan Africa, certain Pacific islands including Hawaii, Marianna islands and Tahiti, and is often intercepted on the mainland US, sometimes triggering eradication programs [5]. Bactrocera dorsalis was recently synonymized to include Bactrocera invadens Drew, Tsuruta & White, Bactrocera papayae Drew & Hancock, and Bactrocera philippinensis Drew & Hancock [3]. With the synonymization of B. dorsalis, there may be over 470 fruit and vegetable species to regulate if a quarantine is established including many commercially important crops [6].…”

Evaluation of Fruit Fly (Diptera: Tephritidae) Monitoring Systems on Mango in Limpopo Province, South Africa

“…In South Africa, three Ceratitis species pose a significant threat to fruit industries, namely, the Marula fruit fly-Ceratitis (Ceratalaspis) cosyra (Walker), which is especially significant in terms of mango production and is usually the most abundant species in mango orchards; the Natal fruit fly-Ceratitis (Pterandrus) rosa (Karsch); and the Mediterranean fruit fly-Ceratitis (Ceratitis) capitata (Wiedemann) [9,10]. The oriental fruit fly-Bactrocera dorsalis (Hendel) was detected in Africa for the first time in Kenya in 2003; it initially was described as B. invadens Drew, Tsuruta and White and now synonymised with B. dorsalis [2,11]. Since the arrival of B. dorsalis in Africa, it has rapidly spread throughout the African continent into many newly-invaded fruit-producing countries [5,12].…”