Comparative sensitivity to methyl eugenol of four putative Bactrocera dorsalis complex sibling species – further evidence that they belong to one and the same species B. dorsalis

Abstract

Males of certain species belonging to the Bactrocera dorsalis complex are strongly attracted to, and readily feed on methyl eugenol (ME), a plant secondary compound that is found in over 480 plant species worldwide. Amongst those species is one of the world’s most severe fruit pests the Oriental fruit fly, Bactrocera dorsalis s.s., and the former taxonomic species Bactrocera invadens, Bactrocera papayae and Bactrocera philippinensis. The latter species have been recently synonymised with Bactrocera dorsalis based on their very similar morphology, mating compatibility, molecular genetics and identical sex pheromones following consumption of ME. Previous studies have shown that male fruit fly responsiveness to lures is a unique phenomenon that is dose species-specific, besides showing a close correlation to sexual maturity attainment. This led us to use ME sensitivity as a behavioural parameter to test if Bactrocera dorsalis and the three former taxonomic species had similar sensitivity towards odours of ME. Using Probit analysis, we estimated the median dose of ME required to elicit species’ positive response in 50% of each population tested (ED50). ED50 values were compared between Bactrocera dorsalis and the former species. Our results showed no significant differences between Bactrocera dorsalis s.s., and the former Bactrocera invadens, Bactrocera papayae and Bactrocera philippinensis in their response to ME. We consider that the Bactrocera males’ sensitivity to ME may be a useful behavioural parameter for species delimitation and, in addition to other integrative taxonomic tools used, provides further supportive evidence that the four taxa belong to one and the same biological species, Bactrocera dorsalis.

Resolving cryptic species complexes of major tephritid pests

“…The four ccomplex members had identical volatile emission profiles and rectal pheromonal components consisting of 2-allyl-3,4, (DMP)dimethoxyphenol and (E-CF)E-coniferyl alcohol (Tan et al 2011, 2013), and the ratios of DMP: E -CF were not significantly different between the different members. Probit analysis showed that the responsiveness of these four members to ME was similar as their ED 50 values (= dose at which 50 % of the population responded) were not significantly different (Hee et al 2015a). However, differences were found for Bactrocera carambolae .…”

The Complete Mitochondrial Genome of Bactrocera carambolae (Diptera: Tephritidae): Genome Description and Phylogenetic Implications

“…invadens'). Their status has been verified by taxonomists and the insect materials have been used in several research projects [11,[17][18][19][20]69].…”

“…invadens') as B. dorsalis. The latter taxonomic revision was supported by multidisciplinary evidence from morphological, morphometric, molecular/genetic, cytogenetic, behavioral/sexual compatibility and chemo-ecological studies [8][9][10][11][12][13][14][15][16][17][18][19][20][21]. However, the synonymization by Schutze et al [8] was criticized [22] and debated [23].…”

Tephritid Integrative Taxonomy: Where We Are Now, with a Focus on the Resolution of Three Tropical Fruit Fly Species Complexes

“…For instance, as part of the CRP, populations of B. dorsalis, B. carambolae, B. papayae, and B. philippinensis were established at the IAEA Insect Pest Control Laboratory in Seibersdorf, Austria. Cultures were subsequently used not only for mating compatibility trials (80) but also for cytogenetics (4) and parapheromone responses (40). Ensuring that each culture line represented its purported taxon was imperative.…”