Scenario of the spread of the invasive species Zaprionus indianus Gupta, 1970 (Diptera, Drosophilidae) in Brazil

Pest categorisation of Zaprionus indianus

The EFSA Panel on Plant Health performed a pest categorisation of Zaprionus indianus (Diptera: Drosophilidae), the African fig fly for the territory of the EU. This species successfully colonised the Indian subcontinent more than four decades ago, and more recently South and North America. Within the EU, the pest occurs in Cyprus, Malta, Portugal (Madeira) and Spain (Canary Islands and Andalusia). Z. indianus is not listed in Annex II of Commission Implementing Regulation (EU) 2019/2072. The larvae of this fly feed on more than 80 plant species both cultivated and non-cultivated. Females produce around 60-70 eggs. Egg laying mostly occurs in decaying fruit or fruit with injuries or mechanical damage. However, Z. indianus can oviposit on undamaged healthy fruit such as figs, strawberries and guavas which provide a potential pathway for entry into the EU. Lower temperature thresholds are around 9-10°C. Optimum development occurs at 28°C. The number of generations per year varies from 12 to 16. Climatic conditions in many EU member states and host plant availability in those areas are conducive for establishment. The introduction of Z. indianus is expected to have an economic impact in the EU especially on fig and strawberry production. Damage caused by other fruit flies (Drosophilidae and Tephritidae) could be increased by mixed infestations. Phytosanitary measures are available to reduce the likelihood of entry and further spread. Z. indianus satisfies all of the criteria that are within the remit of EFSA to assess for it to be regarded as a potential Union quarantine pest.

Insights into differential activity patterns of drosophilids under semi-natural conditions

We showed recently that Drosophila ananassae, a closely related and sympatric species of the commonly studied fruitfly D. melanogaster, shows distinctly deviant patterns in circadian activity/rest rhythm from the latter under a variety of laboratory conditions. To examine whether such differences extend to more natural conditions where a variety of time cues and similar environmental pressures might force different species to adopt similar temporal patterns, we examined these two species under semi-natural conditions over a span of 1.5 years. Furthermore, we asked to what extent features of activity/rest rhythm of flies are conserved across species under changing environmental conditions encountered across seasons, and to do so, we studied two more drosophilid species. We found that while each species exhibits seasonality in activity patterns, this seasonality is marked by interesting inter-specific differences. Similar to laboratory studies, D. ananassae showed activity mostly during the day, while D. melanogaster and D. malerkotliana exhibited almost similar activity patterns across seasons, with predominantly two peaks of activity, one in the morning and another in the evening. Throughout the year, Zaprionus indianus displayed very low levels of activity compared with D. melanogaster, yet, compared with those seen in standard laboratory assays, this species exhibited more robust rhythms under semi-natural conditions. We hypothesise that different ecological factors may have influenced these species to adopt different temporal niches.

Taxonomic and evolutionary analysis of Zaprionus indianus and its colonization of Palearctic and Neotropical regions

Zaprionus indianus is a dipteran (Drosophilidae) with a wide distribution throughout the tropics and temperate Palearctic and Nearctic regions. There have been proposals to reclassify the genus Zaprionus as a subgenus or group of the genus Drosophila because various molecular markers have indicated a close relationship between Zaprionus species and the immigrans-Hirtodrosophila radiation within Drosophila. These markers, together with alloenzymes and quantitative traits, have been used to describe the probable scenario for the expansion of Zaprionus indianus from its center of dispersal (Africa) to regions of Asia (ancient dispersal) and the Americas (recent dispersal). The introduction of Z. indianus into Brazil was first reported in 1999 and the current consensus is that the introduced flies came from high-latitude African populations through the importation of fruit. Once in Brazil, Z. indianus spread rapidly throughout the Southeast and then to the rest of the country, in association with highway-based fruit commerce. These and other aspects of the evolutionary biology of Z. indianus are addressed in this review, including a description of a probable route for this species’ dispersal during its recent expansion.

Tropical Africa as a cradle for horizontal transfers of transposable elements between species of the genera Drosophila and Zaprionus

We have recently reported numerous cases of horizontal transfers of transposable elements between species of drosophilids. These studies revealed a substantial number of horizontal transfers between species of the subgroup melanogaster of the genus Drosophila and between these species and species of the genus Zaprionus. In this review, these transfers and similar, previously reported events are discussed and reanalysed to portray the interrelationships between the species that allowed the occurrence of so many horizontal transfers. The paper also addresses problems that may arise in drawing inferences about the time period during which the horizontal transfers occurred and the factors that may be associated with these transfers are discussed.