Molecular analysis and biodiversity survey of fruit flies associated with deciduous fruits and vines, with focus on economically important species

Research in the field of biological invasions has increased dramatically in the last two decades, especially due to the impact of human activity such as, transport, travel and international trade. Different stages of invasion have been proposed, each stage posing different barriers that must be overcome by the organism for it to become established. For the prevention of new invasions and the formulation of a successful integrated pest management program (IPM), knowledge of natural species community assemblage, movement patterns and the ability to identify the pest species rapidly in the field. In this project we made use of multiple agricultural important fruit fly species, Ceratitis capitata, C. rosa and Bactrocera invadens (B. dorsalis), in the Tephritidae family in different stages of the invasion process using different research methods to (i) investigate seasonal variation in fruit fly abundance in orchards and natural vegetation in the Western Cape to determine whether natural vegetation is used as possible refugia; (ii) determine the suitability of Loop-mediated isothermal AMPlification of DNA (LAMP) to identify Bactrocera invadens (B. dorsalis) rapidly in the field; (iii) to investigate the population genetic structure, using molecular and morphological markers, to estimate gene flow and dispersal ability of C. rosa in South Africa.

Trapping of fruit flies using traps baited with Quest lure, Cue lure, Olive fruit fly lure and Biolure was conducted between February 2012 and March 2013 in orchards and adjacent natural vegetation in the Western Cape Province. LAMP primers based on the Ribosomal gene sequences for the ITS1-5.8S-ITS2 region was designed and tested for Bactrocera invadens (B. dorsalis). Ceratitis rosa, sampled from 22 South African locations, were genotyped at 12 polymorphic microsatellite loci and assessed morphologically using geometric shape analysis of wings to investigate patterns of population structure and determine connectedness of pest-occupied sites.

Results showed that C. capitata was the most abundant species captured and Biolure® the most effective lure. The largest number of individuals of either species (C. rosa and C. capitata) were captured in austral autumn (March-May) in both orchards and natural habitat with low capture rates throughout the rest of the year. Orchards and natural habitats were significantly different with higher trap catches always found in orchards.  Loop-mediated isothermal AMPlification of DNA (LAMP) showed to be marginally adept to identify B. invadens (B. dorsalis), but further work is required to refine this technique. Based on microsatellite markers and geometric morphometrics, results indicate that there is no population structure in C. rosa within South Africa.

This indicates that there are high levels of connectivity between different pest-occupied sites within the country and suggests that area-wide pest management should be undertaken on a much larger, preferably country-wide, scale. My results are discussed in the framework of invasion biology as well as integrated pest management. In conclusion, when investigating biological invasions, information from organismal biology and ecology as well as molecular biology can be valuable to inform decision-making regarding prevention and mitigation of pest species.