Different states of eDNA
Environmental DNA can be present in four principal states described in Figure 1. Here we focus on eukaryotic extra-organismal eDNA9, which is commonly analysed to make accurate inferences as to whether or not a targeted species (usually of conservation or management concern) or community was present at time of sampling16. Additionally, we focus on eDNA states at the cellular level and below because all eukaryotic life forms have cells as a basic unit encapsulating DNA. We recognize that extra-organismal eDNA may also originate from even more complex structures such as tissues and gametes, but variations in these structures are complex across eukaryotes and beyond the scope of what we address in this perspective. However, this variation in tissues and other structures is likely a main factor that contributes to species-specific rates of DNA degradation and persistence.