Diet type and prey preference of predators affect intraguild predation between Amblyseius andersoni and Neoseiulus barkeri

Abstract Amblyseius andersoni and Neoseiulus barkeri, two species of phytoseiid mites that are widely used for the control of small sucking pests, were found to co-occur on Chinese wolfberry in Inner Mongolia. We investigated the possibility of intraguild predation (IGP) between A. andersoni and N. barkeri to explore the interactions and coexistence of these two species. Predation and oviposition of the two predators on heterospecific juveniles were measured and compared with Tetranychus truncatus or Typha pollen as food, or without alternative food. The mortality rate of N. barkeri juveniles was not affected by the diet treatment, but that of A. andersoni juveniles was reduced by the presence of spider mites. The presence of spider mites also increased oviposition by A. andersoni but not by N. barkeri, and the presence of pollen had no influence on the oviposition of the two predators. Thus, according to the IGP criteria for gaining benefits from predation on heterospecific juveniles, it was concluded that IGP between A. andersoni and N. barkeri occurred, with A. andersoni as intraguild predator and N. barkeri as intraguild prey when spider mites were present. In a further choice test in which heterospecific juveniles and T. truncatus juveniles were provided for each predator, female A. andersoni preferred to prey on N. barkeri rather than on spider mites, whereas female N. barkeri preferred to feed on spider mites rather than on A. andersoni. These findings indicate that the higher preference of N. barkeri on T. truncatus might result in its lower predation on the other predator species compared with A. andersoni and, thus, increased the possibility of the coexistence of the two predator species. Therefore, the occurrence of IGP between A. andersoni and N. barkeri appears to be influenced by the availability and type of the diet and the prey preference of the predators.