Host resistance mediated host adaptation and its influence on parasitism in an ectoparasitoid wasp

BACKGROUND Parasitoid wasps often face higher mortality when trying to paralyze resistant hosts, a challenge with important consequences for host adaptation and biological control management. This study explores the ability of Sclerodermus guani , an ectoparasitoid, to adapt plastically by examining how rearing on hosts with varying resistance levels affects parasitism success and behavior. RESULTS Two distinct wasp lineages were established: a stressful lineage (referred to as Ma wasp), continuously reared on resistant, nonheat‐shocked Monochamus alternatus (Ma) larvae, and a permissive lineage (referred to as MaHS wasp), derived from the Ma wasp and reared on less‐resistant, heat‐shocked Ma (MaHS) larvae. Host preference assays showed that Ma wasps consistently preferred Ma larvae, whereas MaHS wasps displayed a significantly reduced preference for Ma larvae, with a notable shift by the tenth generation. When exposed to both Ma and MaHS larvae, MaHS wasps exhibited lower mortality and a higher population growth index than Ma wasps, indicating differences in host resistance. After ten generations of continuous rearing, the fitness of MaHS wasps on Ma larvae was significantly lower than that of Ma wasps. Behavioral assays further demonstrated that Ma wasps were more efficient at locating new hosts than MaHS wasps. CONCLUSION These findings highlight the role of host resistance in parasitoid adaptation and emphasize the importance of host selection in the mass rearing of biological control agents. This research offers valuable insights for optimizing rearing methods to enhance biocontrol effectiveness.