While conservation management has made tremendous strides in the last few decades, the decision of knowing where and how to invest (often) small surveying budgets for biodiversity data collection remains a central hurdle for impactful conservation decision making. New analytical tools, such as environmental DNA (eDNA), are now facilitating broader biodiversity monitoring to take place at unprecedented scales, in part due to its time-efficient, and presumably cost-efficient, premise. eDNA approaches vary from conventional PCR (detecting presence/absence of species), metabarcoding (community structure), to qPCR (relative DNA abundance), and knowing when to employ these techniques over traditional sampling protocols could enable conservation practitioners to make informed trade-offs between cost, accuracy, and speed of data collection. Using 12 species-specific primers designed for conventional PCR use in eDNA analysis of the Yangtze Finless Porpoise (Neophocaena asiaeorientalis asiaeorientalis), a critically endangered aquatic mammal within the Yangtze River, we validated and optimized these same primers for use in real-time Quantitative PCR (qPCR). We tested the repeatability and sensitivity of primer each to detect YFP eDNA and subsequently compared the cost of traditional visual sampling to both conventional PCR and qPCR eDNA tools. Our results suggest qPCR to be substantially more sensitive than conventional PCR eDNA analysis, although the later remains the least-expensive sampling option. Still, due to a lack of sensitivity causing an increased probability of false negatives, conventional PCR may not be the most robust sampling method for this taxa and should only be employed as a supplementary tool or when large populations are expected to be present. Alternatively, utilizing qPCR for eDNA protocols is still less-expensive than visual surveying and represents a highly repeatable and sensitive method for this behaviorally elusive species. Presenting a cost assessment of eDNA to traditional surveying practices has scarcely been discussed, while contrasting deliverables to the cost of different eDNA methods has, to date, been ignored. Yet given budgetary constraints, particularly for developing countries where low-governance and high endemism are present, we encourage managers to carefully consider the trade-offs among data accuracy, cost, coverage and speed for biodiversity collections.
An experimental assessment of the distribution of environmental DNA along the water column
