New invasion or expansion: evaluating the genetic relationships of Bactrocera dorsalis

Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), the oriental fruit fly, is a highly invasive species that has occasionally been detected in Florida, where conditions are highly favorable for the establishment of this pest. In 2015, a major infestation of B. dorsalis was detected in the Redland agricultural area of Miami-Dade county. Other detections of this pest have occurred in various locations in Florida, including the Redland area, before and after 2015. Questions arose whether any of these detections were related to the major infestation in Redland in 2015, possibly as one or more small, scattered populations that went undetected over time only to resurge as better conditions arose. To address this question, the genetic variation of the 2015 Redland outbreak was characterized using microsatellite DNA and by sequencing a portion of the mitochondrial cytochrome oxidase I (COI) gene. Population structure analyses and exclusion testing was performed on flies captured in years immediately preceding and after 2015 using microsatellites to determine (1) if flies were inconsistent with a shared source and (2) if the 2015 population could be excluded as source of subsequent captures. The COI sequences of the flies also were compared to determine if the 2015 outbreaks could explain variation in subsequent years. Results from this study found that flies captured before and after 2015 were not related to the population eradicated in Redland in 2015. Therefore, we concluded that flies captured in Florida between 2014 and 2021 were not part of any single, continuous breeding population that persisted over months.