Genomic Insights Into the Evolution of Parental Care in Weevils.

Parental care, a key step in the evolution of sociality, has evolved multiple times in insects, yet the molecular mechanisms underlying its emergence remain poorly understood. Weevils (Curculionidae) exhibit diverse parental care behaviors, from nest building to egg and larval attendance, making them an ideal system to investigate genomic changes associated with social behavior. We analyzed 13 high-quality weevil genomes, encompassing independent origins of egg and larval attendance, to test two predictions: (i) the sheltering hypothesis, where parental care relaxes selection on traits critical for independent larval survival and (2) the regulatory hypothesis, where behavioral shifts are driven by changes in transcriptional regulation. In support of hypothesis 1, we identified over 400 genes with evidence of significantly relaxed selection on the branches where egg and larval attendance evolved. In further support, we uncovered a significant number of convergent gene losses that coincided with both origins of larval attendance, particularly in genes linked to transcriptional regulation, metabolism and development. In contrast, positive selection and intensified selection were rare but contained multiple genes regulating gene expression, consistent with hypothesis 2. Together, these results suggest that parental care in weevils drives both simplification of larval traits through relaxed selection and convergent gene loss, and innovation in caregiving behaviors via adaptive changes in gene regulation.