Looking to the past to inform the future: What eDNA from herbarium specimens can tell us about plant-animal...

The importance of natural history collections in modern ecological and genetic research cannot be overstated. Herbarium specimens provide historical information that can be used to investigate community ecology, phenology, and population genetics. In this study, environmental DNA (eDNA) metabarcoding and next-generation sequencing were used to test the efficacy of detecting historical plant-animal interactions from herbarium specimen flowers.

A modified eDNA isolation method and standard Illumina sequencing protocols were used. Animal eDNA was amplified using both cytochrome c oxidase subunit I (COI) and 16S primers to increase detection probability. The relationship between specimen age (0-69 years) and target taxa read depth was also investigated.

We generated and identified over 1.5 million sequences of animal taxa belonging to 29 clades (families or orders). These methods enabled the detection of taxa including birds, mammals, hymenopterans, lepidopterans, coleopterans, and taxa belonging to "intrafloral" communities. While herbarium specimens overall yielded less identifiable eDNA compared to fresh material, the age of the herbarium specimen negligibly affected the amount of target and/or non-target eDNA detected in flowers.

With careful consideration of the types of data that may be obtained through sampling eDNA from herbarium specimens, these methods could prove valuable to future research on plant-animal interactions.