Assessing environmental DNA metabarcoding and camera trap surveys as complementary tools for biomonitoring of remote desert water bodies

Biodiversity assessments are indispensable tools for planning and
monitoring conservation strategies. Camera traps (CT) are widely used to
monitor wildlife and have proven their usefulness. Environmental DNA
(eDNA)-based approaches are increasingly implemented for biomonitoring,
combining sensitivity, high taxonomic coverage and resolution,
non-invasiveness and easiness of sampling, but remain challenging for
terrestrial fauna. However, in remote desert areas where scattered water
bodies attract terrestrial species, which release their DNA into the
water, this method presents a unique opportunity for their detection. In
order to identify the most efficient method for a given study system,
comparative studies are needed. Here, we compare CT and DNA metabarcoding
of water samples collected from two desert ecosystems, the Trans-Altai
Gobi in Mongolia and the Kalahari in Botswana. We recorded with CT the
visiting patterns of wildlife and studied the correlation with the
biodiversity captured with the eDNA approach. The aim of the present study
was threefold: a) to investigate how well waterborne eDNA captures signals
of terrestrial fauna in remote desert environments, which have been so far
neglected in terms of biomonitoring efforts; b) to compare two distinct
approaches for biomonitoring in such environments and c) to draw
recommendations for future eDNA-based biomonitoring. We found significant
correlations between the two methodologies and describe a detectability
score based on variables extracted from CT data and the visiting patterns
of wildlife. This supports the use of eDNA-based biomonitoring in these
ecosystems and encourages further research to integrate the methodology in
the planning and monitoring of conservation strategies.