An invasive species complex, or just one busy fly? Coming to grips with the Bactrocera dorsalis complex

The Bactrocera dorsalis complex of tropical fruit flies includes a number of known invasive species, including B. dorsalis s.s., B. papayae and B. invadens. Most of the species in the complex were split from B. dorsalis s.s. in a 1989 taxonomic revision. Since then attempts to develop robust diagnostics for the majority of these pest species have failed. This is particularly a problem in the Asia/Pacific region where multiple species may be encountered and accurate species identification is required for border security, emergency response, international market access and SIT. At the crux of the problem lies an issue about the biological validity of the taxonomic species. Is failure to develop robust diagnostics a technical issue still to be resolved, or are the diagnostic results reflecting the fact that the taxonomic species are not biologically valid (i.e. the group has been split too far)? In this talk we present the results of an ongoing study to define the species limits of the pest species in the B. dorsalis complex. A ‘multiple line of evidence’ approach is being used, which includes concurrent morphological, genetical, behavioural and physiological experiments. Results to date suggest that while some taxa in the complex are probably biologically valid, others are not.