Genetic Differentiation of a New World Screwworm Fly Population from Uruguay Detected by SNPs, Mitochondrial DNA and Microsatellites in Two Consecutive Years

SIMPLE SUMMARY: The New World screwworm (NWS) fly is a pest related to economic impacts in livestock breeding, mainly because females lay their eggs in wounds and natural cavities of warm-blooded vertebrates. A direct way to control this pest is the sterile insect technique (SIT), which is based on the release of sexually sterilized males to mate with wild females, resulting in the absence of new flies. The first step to the implementation of such program is to know how flies’ populations are structured, that is, if they can freely mate in the field or, otherwise, if they are impeded of mate due to spatial or temporal barriers. Here we investigated genomic polymorphisms to infer temporal structure in a population of the NWS fly from Uruguay in two consecutive years (approximately 18 generations). We found that this time was enough for this population to change its genetic composition, but it was not sufficient to prevent free mate among individuals from one year to the next. We also found signal that some of the polymorphisms are related to the response of the population to insecticide chemical control. This approach can be used in the future to estimate spatial barriers to geographically isolated populations. ABSTRACT: The New World screwworm (NWS) fly, Cochliomyia hominivorax (Diptera: Calliphoridae), is an economically important ectoparasite currently distributed in South America and in the Caribbean basin. The successful eradication of this species in USA, Mexico and continental Central America was achieved by a control program based on the sterile insect technique (SIT). In order to implement a genetic control strategy over the NWS fly’s current area of occurrence, first, it is necessary to understand the species dynamics and population structure. In order to address this objective, the spatial genetic structure of the NWS fly was previously reported in South America based on different genetic markers; however, to date, no study has investigated temporal changes in the genetic composition of its populations. In the current study, the temporal genetic structure of a NWS fly population from Uruguay was investigated through two consecutive samplings from the same locality over an interval of approximately 18 generations. The genetic structure was accessed with neutral and under selection SNPs obtained with genotyping-by-sequencing. The results gathered with these data were compared to estimates achieved with mitochondrial DNA sequences and eight microsatellite markers. Temporal changes in the genetic composition were revealed by all three molecular markers, which may be attributed to seasonal changes in the NWS fly’s southern distribution. SNPs were employed for the first time for estimating the genetic structure in a NWS fly population; these results provide new clues and perspectives on its population genetic structure. This approach could have significant implications for the planning and implementation of management programs.