Genetic diversity of the predatory mite Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae) with an overview of its distribution and implications for biological control

Amblyseius swirskii is a predatory mite of the family Phytoseiidae that is widely used in biological control of small insect and mite pests. A population from Israel was the source of material now commercially marketed by several biocontrol companies. The present study aimed to characterize the genetic variability of A. swirskii using 12S rRNA, CytB and COI mtDNA sequences, and explore its geographical distribution based on a compilation of known and newly- reported occurrences, including populations from several countries where this species naturally occurs. Amblyseius swirskii is reported from 22 countries, primarily in the eastern Mediterranean basin and Africa. The species has been reported on 48 plant families, with the highest number of observations on Rosaceae, Rutaceae and Solanaceae, mostly on crops, but also on uncultivated plants. The genetic diversity of A. swirskii was very low in all populations except the one from Cape Verde; all other studied populations were not differentiated from the commercial ones. The results suggest that commercialized and natural populations now co-occur widely, even in natural environments. The Cape Verde population seems to be a distinct natural population with relatively high intra-population variation, even among specimens collected in a single locality and on a single plant species. Further analyses would be required to determine how much the observed genetic differentiation results in different biological features, but the diversity present in the natural Cape Verde populations of A. swirskii may provide a source of novel traits with potential to improve the performance of this natural enemy.