Include information and recommendation on inferring absences.

[tobiasgf]

The guide should include recommendations and information on when it is adequte to infer absence using eDNA methods.

• I have a feeling that it is broadly accepted that simple metabarcoding is not adequate to infer absences (i.e. interpreting zero reads as absence), and that some validated assay (with replicates etc) is required. There must be some research to cite.
• qPCR - on the other hand - is more often used for this particular aim.

(one place to start: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0285674)