Ancient DNA from ice age insects: proceed with caution

The paucity of ancient DNA (aDNA) studies in insects can be traced to the dismissal of the 1990s reports of DNA isolation from amber-entombed insects. In retrospect, amber was an obvious place to start, but it has since been demonstrated that DNA preservation is not necessarily correlated with physical preservation. The discipline of aDNA is rapidly progressing as issues regarding contamination with modern sequences and detection of DNA damage are addressed. Two major concerns in ancient DNA studies are the co-purification of DNA polymerase inhibitors and the presence of DNA lesions. Preliminary data demonstrate DNA extraction is possible from beetle remains isolated from packrat middens. Although specimens from permafrost sediments and ancient rodent middens are potential sources of aDNA, collection and curation procedures require modification to minimize contamination and optimize DNA yield. Since aDNA isolation in insects requires the complete destruction of fossil material, another consideration is the taxonomic groups that are adequately represented to justify the sacrifice of geological specimens. Although most recommended aDNA authentication procedures are easily followed, some are impossible for insect samples due to their small size, making the establishment of authentication procedures of aDNA from small samples a final consideration.