Genomic Expansion and Adaptation in a Parasitoid Wasp Eretmocerus hayati (Hymenoptera: Aphelinidae)

The parasitic wasps of Aphelinidae (Hymenoptera) are a group of insects with significant biological control value. However, their genomic evolution and ecological adaptation mechanisms remain unclear. In this study, we focused on the genome analysis of Eretmocerus hayati and performed a comparative analysis with four other species from Aphelinidae. Our results indicated that the divergence time of Aphelinidae was approximately 119.9 million years ago. In Er. hayati, gene families related to energy metabolism and humoral immunity have significantly expanded, which may be associated with the high metabolic demands of its small body size and the immune adaptation strategies resulting from its unique parasitic methods. Additionally, genes involved in DNA replication and recombination have undergone positive selection in the ancestral branch of Aphelinidae species. Compared with 23 species within nine families in the Chalcidoidea superfamily studied here, the genome size of Er. hayati is the largest. The analysis of repetitive sequences revealed a recent burst of long terminal repeat (LTR) sequence insertions in the genome of Er. hayati. Our study indicates the evolutionary characteristics of Er. hayati in terms of gene family evolution, chromosomal collinearity, and transposon dynamics, providing a theoretical basis for understanding the environmental adaptation and biological control applications.