eDNA Assessment of the Diamond Darter (Crystallaria cincotta) in its Current and Historic Distribution Range

Investigations of Diamond Darter (Crystallaria cincotta) distributions through environmental DNA (eDNA) sampling may serve as an emergent monitoring tool specifically for this species. The Diamond Darter is a federally endangered fish of the Ohio River basin extant only in West Virginia. The cryptic behavior and incomplete comprehension of this species serve as perfect grounds to test if eDNA can serve as an efficient means of species detection. The objective of this study was to determine Diamond Darter occupancy within current and historical distributions of its range through eDNA investigations with a potential for alterations in the species’ current recognized range. We developed a unique single nucleotide polymorphism (SNP) that identifies Diamond Darter DNA distinctly from 23 other Percid species including the Crystal Darter (Crystallaria asprella). Collected eDNA was paired against this SNP to identify locations where the organism persists. Various locations throughout the current and historical ranges of the Diamond Darter were sampled through water filtrations and examined to determine presence of target species DNA. 137 samples across 38 sites in six watersheds among four states were administered resulting in multiple positive detections primarily within the current critical habitat designation of the lower Elk River in West Virginia. Follow-up nighttime spotlight surveys at positive detection sites proved successful at observing Diamond Darter individuals, as well as the discovery of a new site locality for the species. Ultimately, our sampling efforts have provided sound evidence supporting significant contributions towards conservation efforts and distribution mapping of the Diamond Darter through eDNA.