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Tuesday, January 30 • 6:00pm - 9:00pm
Poster Display. Sampling Designs for Landscape-level eDNA Monitoring Programs Using Three-level Occurrence Models

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AUTHORS: Erica L. Mize, Whitney Genetics Laboratory, Midwest Fisheries Center, U.S. Fish & Wildlife Service; Christopher M. Merkes, Upper Midwest Environmental Sciences Center, U.S. Geological Survey; Richard A. Erickson, Upper Midwest Environmental Sciences Center, U.S. Geological Survey

ABSTRACT: Natural resource managers conduct landscape-level monitoring using environmental DNA (eDNA)-based sampling approaches. Analyzing eDNA-based sampling data requires addressing three probabilities: the probability of occurrence of eDNA at a site, the probability of occurrence of eDNA within a sample, and the probability of molecular detection. Occurrence (or synonymous occupancy) models allow the estimation of these probabilities. However, most occupancy models and guidance for their application do not consider subsampling and replication across multiple-levels. We examined subsampling and replication cross multiple levels with four approaches. First, we examined how many samples would be required to detect eDNA at a site. Second, we examined how well the three-level occurrence model could compare relative abundance across sites. Third, we examined the best balance of replication between sample collection and molecular analysis. Fourth, we examined how well a three-level occupancy model can recover known parameters from simulated datasets. We used a simulation study and mathematical probability calculations to gain insight into the model and possible study designs. We found that comparing the relative abundance of a common species requires less replication than reliable detection of a rare species. For example, under low occurrence and low detection situations, 16 molecular replicates and 75 samples per site may be required to consistently detect rare species. Conversely, estimating and comparing occurrence and detection probabilities under better conditions may only require 4 molecular replicates and 20-30 samples per site. More broadly, our findings illustrate the importance of considering study design and sample sizes when planning eDNA-based research, monitoring, and management.

Tuesday January 30, 2018 6:00pm - 9:00pm CST
Ballroom C & Foyer