Population-specific cold tolerance of the predatory miteAmblydromalus limonicus

Abstract: Since 2015, the predatory mite Amblydromalus limonicus, which is exotic toEurope, is registered for use as biocontrol agent against thrips in protected crops in Austria.One advantage of A. limonicus over other commercially available thrips predators is its coldtolerance, allowing release of the predator early in the growing season. This trait ofA. limonicus, however, could also allow its overwintering and establishment in Austria underthe predicted temperature increase due to global climate change in Europe until 2100.Therefore, we evaluated the diapause potential, the egg hatchability at 8 and 10 °C, andjuvenile development and oviposition at 10 °C of A. limonicus from three populations(KO = population from the commercial producer Koppert; SP = alien population establishedin Spain since 2011; NZ = native population collected 2014 in Auckland, New Zealand).Irrespective of population, the females were not able to enter diapause under short dayconditions (8 h light, 16 h dark). Egg hatchability at 8 °C was nearly zero in all threepopulations. At 10 °C, most eggs hatched and juvenile survival to adulthood did notsignificantly differ between populations. Juveniles of KO and SP reached adulthood earlierthan did juveniles of NZ. Irrespective of population, all females survived the experimentalperiod of 10 days at 10 °C. Females of NZ produced more eggs than those of SP; eggproduction by KO females was intermediate. Our results allow four preliminary conclusions:(1) A. limonicus is a relatively cold-tolerant predatory mite species but not able to enterdiapause; (2) its cold-tolerance may allow a head-start in population growth early in theseason, as compared to native species, in case of temporary establishment in Austria; (3) cold-toleranceof A. limonicus seems a conserved species-specific trait; (4) since populationdifferences in cold tolerance were negligible, additional life history and behavioural traitsmust be taken into account for predicting which population has the highest potential to invadeAustrian predatory mite communities.Extended abstract