Environmental RNA applications and their associated gene targets for management and conservation

Abstract Environmental DNA (eDNA) analysis is now a widely‐used tool to non‐invasively monitor a variety of organisms. However, eDNA applications are limited with respect to gaining information on population demography and the status of individuals within a population. Although in its infancy, environmental RNA (eRNA) analysis has the potential to reveal information about populations that may be important for conservation or management decisions. Using gene databases and current literature, we synthesized information about gene products that may be useful eRNA targets for environmental samples focusing on the model organisms Danio rerio (zebrafish), Xenopus laevis (African clawed frog), and X. tropicalis (Western clawed frog). We suggested that appropriate gene products must be expressed in tissues thought to contribute to environmental samples, must be exclusively expressed or upregulated by at least 2‐fold in portions of populations (e.g., a single age class), and must be useful to a relevant application for population monitoring. We categorized 127 total eRNA targets based on their potential applications: distinguishing and quantifying living communities, determining population age structure, determining sex ratios, and assessing population health. There are many uncertainties and current limitations that need to be addressed before eRNA can be an established method in population management including understanding the ecology of eRNA, determining methods for determining assay specificity, and applying what we know from model organisms to other species. However, we see immense potential in the utility of eRNA in gathering population‐level information and serving as an important tool for managers in the near future.