Tracking the origins of fly invasions; using mitochondrial haplotype diversity to identify potential source populations in two genetically intertwined fruit fly species (Bactrocera carambolae and B. dorsalis)

Authors: SAN JOSE, MICHAEL - University Of Hawaii; DOORENWEERD, CAMIEL - University Of Hawaii; LEBLANC, LUC - University Of Idaho; BARR, NORMAN - Animal And Plant Health Inspection Service (APHIS); Geib, Scott; RUBINOFF, DANIEL - University Of Hawaii

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/16/2018
Publication Date: 9/21/2018
Citation: San Jose, M., Doorenweerd, C., Leblanc, L., Barr, N., Geib, S.M., Rubinoff, D. 2018. Tracking the origins of fly invasions; using mitochondrial haplotype diversity to identify potential source populations in two genetically intertwined fruit fly species (Bactrocera carambolae and B. dorsalis). Journal of Economic Entomology. 111(6):2914-2926. https://doi.org/10.1093/jee/toy272.
DOI: https://doi.org/10.1093/jee/toy272

Interpretive Summary: The carambola and oriental fruit flies are important pests of many tropical and subtropical fruits. These flies have spread across the world through global travel and trade, and new areas are are at risk of invasion. Whenever new invasive populations are discovered, quick and accurate identification is needed to mitigate the damage they can cause. Determining the invasive pathways by which species travel can prevent further spread of pests as well as subsequent reinvasions through the same pathway. Using sequencing of the barcode region (cytochrome oxidase I), we examined the diversity and structure of over 1500 individual specimens of these species from 18 distinct geographic locations. Our findings showed a lack of genetic structure tied to geographic source of these species, as well as some level of genetic exchange between the species. Extremely high levels of genetic diversity of the samples also suggest we do not yet have a complete sampling of the true diversity of these species from their native ranges. Examining detected samples from California trap catches, no population structure was detected in California, and the majority could not be assigned to a genetic type from Asia. Despite the lack of structure from this study, these results provide a foundation for the accurate determination of the provenance of invasive populations around the world.

Technical Abstract: Bactrocera carambolae Drew and Hancock (The Carambola fruit fly) and B. dorsalis (Hendel) (The Oriental fruit fly) (Diptera: Tephritidae) are important pests of many tropical and subtropical fruits. These flies have spread across the world through global travel and trade, and new areas are are at risk of invasion. Whenever new invasive populations are discovered, quick and accurate identification is needed to mitigate the damage they can cause. Determining the invasive pathways by which species travel can prevent further spread of pests as well as subsequent reinvasions through the same pathway. Molecular markers can be used for both species identification and pathway analysis. We analyzed 1601 individuals from 18 populations using 765 base pairs of the mitochondrial cytochrome oxidase I (COI) gene to infer the haplotype diversity and population structure within these flies from across their native and invasive ranges. We analyzed these samples by either grouping by species or geographic population due to the genetic similarity in the mitochondrial genome. We found no genetic structure between B. dorsalis and B. carambolae and our findings suggest recent and most likely ongoing, genetic exchange between these two species in the wild. Hyper-diverse mitochondrial genetic diversity in the native range suggest large population sizes and high mutation rates. Only 52% of the haplotypes found in the trap captures from California are shared with haplotypes with flies found in our global survey indicating significant genetic diversity in the native range missing in our sampling. However, these results provide a foundation for the accurate determination of the provenance of invasive populations around the world.