Geographic Population Genetic Structure of the New World Screwworm, Cochliomyia hominivorax (Diptera: Calliphoridae), Using SNPs

The New World screwworm, Cochliomyia hominivorax (Coquerel 1858) (Diptera: Calliphoridae), is a serious parasite of livestock, humans, and other warm-blooded animals. It has been eradicated from the northern parts of its historical range down to the Panama-Colombian border where a permanent barrier zone is maintained. This eradication was accomplished through using the sterile insect technique (SIT). In 2016 there was an outbreak of C. hominivorax in the Florida Keys. In only six months, this pest was successfully re-eradicated using SIT, but the geographic origin of the invasion has yet to be resolved. It was previously determined that the Florida flies most likely represented a single invasion, and it was recommended that a finer-scale genetic assessment should be completed. Thus, this current proof-of-concept study aimed to develop a population genetic database using single nucleotide polymorphisms (SNPs) to reference outbreaks and potentially identify the origin of the Florida outbreak. This initial database consists of wild-caught samples from 4 geographic locations as well as laboratory colony samples that originated from 7 additional locations using a genotyping by sequencing (GBS) approach. Geographic population structuring was identified for twelve populations that clustered according to geographic location. The Florida outbreak samples appeared similar to samples from the outer Caribbean cluster which included samples from Dominican Republic and Trinidad and Tobago, however, these results will be further clarified with the replacement of laboratory colony samples with future wild-caught samples.