Masters Thesis

Development of eDNA techniques for the detection of Trachemys scripta in aquatic samples and detection of prey items (Danio rerio) in Trachemys scripta fecal samples

Early detection of invasive species and evaluation of their impact on native ecosystems is key to conservation efforts. The use of environmental DNA (eDNA) has emerged as a useful tool to complement traditional field surveys in studying both the range and the effect of invasive species. eDNA is genetic material released by an organism into the environment; eDNA extracted from environmental samples can be used to determine the location of a species and its distribution, or to identify prey items contained within fecal samples. In this study, I developed eDNA techniques to detect an invasive turtle species, the red-eared slider (Trachemys scripta) in water samples collected under both laboratory and field conditions and to detect specific prey items in fecal samples collected from Trachemys scripta in the laboratory. Turtle detection used qPCR primers designed to target the D-loop region of mitochondria. eDNA in water samples was concentrated onto a cellulose nitrate filter, and extracted DNA was amplified using qPCR. Water samples taken from laboratory aquaria and from a wastewater treatment facility in Chico produced two positive detections. Water samples from another site not known to house turtles, the Sacramento Zoo, produced a weak positive detection. I also detected Danio rerio in fecal samples collected from Trachemys scripta. Zebrafish detection used qPCR primers designed to target the D-loop region of mitochondria. After adding Danio rerio to food pellets in Trachemys scripta‘s diet, I used a PCI precipitation method to extract eDNA from feces and was able to positively identify Danio rerio in fecal samples. For dietary analysis, eDNA provides ecologists with a powerful tool for identifying food items in feces. Of 328 extant species of turtle, approximately 50% are listed as endangered, and many are threatened by invasive species. These techniques for the detection of invasive species and evaluation of their impact can contribute to global turtle conservation efforts.

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