Abstract
An FAO/IAEA Co-ordinated Research Project (CRP) on “Resolution of Cryptic Species Complexes of Tephritid Pests to Overcome Constraints to SIT Application and International Trade” was conducted from 2010 to 2015. As captured in the CRP title, the objective was to undertake targeted research into the systematics and diagnostics of taxonomically challenging fruit fly groups of economic importance. The scientific output was the accurate alignment of biological species with taxonomic names; which led to the applied outcome of assisting FAO and IAEA Member States in overcoming technical constraints to the application of the Sterile Insect Technique (SIT) against pest fruit flies and the facilitation of international agricultural trade. Close to 50 researchers from over 20 countries participated in the CRP, using coordinated, multidisciplinary research to address, within an integrative taxonomic framework, cryptic species complexes of major tephritid pests. The following progress was made for the four complexes selected and studied:Anastrepha fraterculus complex – Eight morphotypes and their geographic and ecological distributions in Latin America were defined. The morphotypes can be considered as distinct biological species on the basis of differences in karyotype, sexual incompatibility, post-mating isolation, cuticular hydrocarbon, pheromone, and molecular analyses. Discriminative taxonomic tools using linear and geometric morphometrics of both adult and larval morphology were developed for this complex.Bactrocera dorsalis complex – Based on genetic, cytogenetic, pheromonal, morphometric, and behavioural data, which showed no or only minor variation between the Asian/African pest fruit flies Bactrocera dorsalis, Bactrocera papayae, Bactrocera philippinensis and Bactrocera invadens, the latter three species were synonymized with Bactrocera dorsalis. Of the five target pest taxa studied, only Bactrocera dorsalis and Bactrocera carambolae remain as scientifically valid names. Molecular and pheromone markers are now available to distinguish Bactrocera dorsalis from Bactrocera carambolae.Ceratitis FAR Complex (Ceratitis fasciventris, Ceratitis anonae, Ceratitis rosa) – Morphology, morphometry, genetic, genomic, pheromone, cuticular hydrocarbon, ecology, behaviour, and developmental physiology data provide evidence for the existence of five different entities within this fruit fly complex from the African region. These are currently recognised as Ceratitis anonae, Ceratitis fasciventris (F1 and F2), Ceratitis rosa and a new species related to Ceratitis rosa (R2). The biological limits within Ceratitis fasciventris (i.e. F1 and F2) are not fully resolved. Microsatellites markers and morphological identification tools for the adult males of the five different FAR entities were developed based on male leg structures.Zeugodacus cucurbitae (formerly Bactrocera (Zeugodacus) cucurbitae) – Genetic variability was studied among melon fly populations throughout its geographic range in Africa and the Asia/Pacific region and found to be limited. Cross-mating studies indicated no incompatibility or sexual isolation. Host preference and genetic studies showed no evidence for the existence of host races. It was concluded that the melon fly does not represent a cryptic species complex, neither with regard to geographic distribution nor to host range. Nevertheless, the higher taxonomic classification under which this species had been placed, by the time the CRP was started, was found to be paraphyletic; as a result the subgenus Zeugodacus was elevated to genus level.
Highlights
Tephritid fruit flies (Diptera: Tephritidae) are among the world’s worst pests of agriculture, being of major economic importance in most tropical, subtropical and temperate countries (Cavalloro 1983, White and Elson-Harris 1994)
Bactrocera cucurbitae was put in a new generic combination: Zeugodacus cucurbitae, and should be referred to by this name onwards (Virgilio et al 2015)
Following an integrative taxonomic approach, the biology, cytogenetics, ecology, morphology, genetics, and physiology of major pest tephritid cryptic species complexes is much better understood. This increased knowledge has resulted in formal decisions on the species status of some taxa within these complexes, facilitating international horticultural trade and simplifing Sterile Insect Technique (SIT) application against pest species of these complexes
Summary
Tephritid fruit flies (Diptera: Tephritidae) are among the world’s worst pests of agriculture, being of major economic importance in most tropical, subtropical and temperate countries (Cavalloro 1983, White and Elson-Harris 1994) By laying their eggs directly into fruit, where the maggots feed and develop, these pest species cause enormous devastation to both food production and international trade in spite of often intensive insecticide applications. On the other hand there is increased demand from Africa, the Asia-Pacific and Latin America to address other major tephritid species or groups of economic importance Some of these major pest fruit fly species occur within cryptic species complexes that include taxonomically described species that may be geographical variants of the same species. During the implementation of the CRP, four Research Co-ordination Meetings (RCMs) were held to review research progress and to agree on future research directions and activities: the first RCM in Vienna, Austria from 2–6 August 2010, the second RCM in Brisbane, Australia from 31 January–3 February 2012, the third RCM in Tucumán, Argentina from 26–31 August 2013 and the fourth and final RCM in La Réunion, France from 1–5 June 2015
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