Aphelinus nigritus‐induced transgenerational fecundity compensation in parasitized Melanaphis sorghi

Abstract

Aphids adopt many defensive strategies against natural enemies. While immediate strategies like emitting alarm pheromones or producing secretions are often researched, fewer studies have assessed long‐term defences that include physiological adaptive responses affecting aphid reproduction. Fecundity compensation is a post‐wounding increase in host reproduction, which benefits the offspring of wounded or parasitized insects. Though fecundity compensation can be expressed by individuals experiencing natural enemy attacks, it can also be transgenerational, wherein the offspring of wounded or parasitized mothers reproduce more than the offspring of unaffected mothers. The possibility of fecundity compensation was tested on laboratory populations of the sorghum aphid (SA), Melanaphis sorghi (Hemiptera: Aphididae), in response to wounding from a needle puncture or sting by Aphelinus nigritus Howard (Hymenoptera: Aphelinidae). No evidence of reproductive compensation was found among needle‐wounded, stung and mummified (successfully parasitized), or stung but not mummified SAs in the parental generation, nor in the F1 generation of needle‐wounded or stung but not mummified aphids. However, transgenerational fecundity compensation was observed in F1 daughters of mummified F0 mothers, though this effect did not occur in the F2 generation. At the molecular level, changes were not detected in the expression of DNA methylation and histone modification genes that potentially mediated transgenerational fecundity compensation in SAs stung by A. nigritus, regardless of whether aphids were successfully parasitized. As SA is a cereal aphid pest, the possibility of fecundity compensation should be tested when assessing the suitability of certain parasitoids as biological control agents.