Mating-Induced Trade-Offs upon Egg Production versus Fertilization and Offspring’s Survival in a Sawfly with Facultative Parthenogenesis

SIMPLE SUMMARY: Study of mating-induced trade-offs between reproduction and survival is conducive to provide evolutionary insights into reproductive strategies and aging. Using RNA sequencing and bioinformatics, we found that mating induced changes of genes and pathways related to reproduction and survival in females of a pine sawfly. Mating induced substantial downregulation on genes associated to immunity, stress response, and longevity. However, mating induced divergent reproductive response, with downregulation on genes related to egg production while upregulation on genes related to egg fertilization. Considering the nature of limited resources in adults, low fecundity and egg protection behavior in this sawfly, we suggest that mating triggers trade-offs between reproduction and survival in this insect and females of this species have evolved specific strategies to adapt to the living conditions, e.g., restrict whole fecundity to ensure higher fertilization and offspring’s survival. ABSTRACT: Investigation of mating-induced trade-offs between reproduction and survival is conducive to provide evolutionary insights into reproductive strategies and aging. Here, we used RNAseq and bioinformatics to reveal mating-induced changes of genes and pathways related to reproduction and survival in female Cephalcia chuxiongica, a pine defoliator with facultative parthenogenesis and long larval dormancy. Results showed that mating induced substantial downregulation on genes and pathways associated to immunity, stress response, and longevity. However, mating induced divergent reproductive response, with downregulation on genes and pathways related to egg production while upregulation on genes and pathways related to egg fertilization. Considering the nature of limited resources in adults, low fecundity, and egg protection behavior in C. chuxiongica, we suggest that mating triggers trade-offs between reproduction and survival in this insect and females of this species may have evolved specific strategies to adapt to the environmental and hosts’ conditions, e.g., restrict whole fecundity to ensure higher fertilization and offspring’s survival. Moreover, mating induced significant responses on genes and pathways that play important roles in vertebrate reproduction while their function in insects are unclear, such as the progesterone-mediated oocyte maturation pathway; the significant regulation after mating suggests that their function may be evolutionarily conserved in animal kingdom.