Resin does not safeguard insect DNA during early decay despite preservation of soft tissues

Abstract

Abstract The notion that plant resin acts as an exceptional preservative of insect DNA and soft tissues—functioning as a natural dehydration capsule—has been questioned in recent years, yet empirical support remains limited. We applied an actuotaphonomic approach across a 30-day time series to assess DNA and internal soft tissue preservation in two model species of insects, i.e., Drosophila melanogaster (Diptera) and Tribolium castaneum (Coleoptera), under two treatments: embedding in fresh pine resin or remaining unembedded and air-dried. Total nucleic acid concentration, relative dsDNA, and quantitative PCR targeting insect and bacterial genes revealed a similar overall DNA decline through time, with no significant differences between treatments, although some resin-embedded replicates degraded faster. Synchrotron tomography showed taxon- and treatment-dependent soft tissue differences. Unembedded specimens of both orders displayed dried internal tissues after 30 days. Resin-embedded fruit flies largely retained intact muscle structure with minimal gas accumulation. Embedded red flour beetles, while maintaining tissue structure, were more poorly preserved, showing diffuse tissue boundaries and abundant gas likely from bacterial metabolism. These findings indicate that soft tissue preservation in pine resin is group-specific, possibly linked to exoskeletal permeability affecting moisture and resin exchange during decay, and suggest that recovering ancient DNA from amber fossil insects is highly improbable.