Graduate Thesis Defense

Name:Mark Spangler
Title:Environmental DNA sampling and spatial modeling as means to investigate wood frog (Rana sylvatica) range extent in northern Alaska
Date:Wednesday, 3 May 2017
Location:Murie Bldg, rm 103/105
Major Professor:Falk Huettmann


Amphibian conservation and management is growing in practice in light of their global decline over the past 30+ years. In northern landscapes, however, amphibians are still under-recognized. What few species occur are typically widespread and common species at the northern extent of their range. It is exactly this mindset that results in a lack of baseline data, impeding their effective management. Under-consideration of the wood frog (Rana sylvatica) in Alaska has resulted in deficient monitoring practices and incomplete distribution knowledge. Here, I develop and recommend for widespread adoption an environmental DNA detection assay for the wood frog at the northern extent of its range. This assay was tested to be species specific, allowing it to be implemented in areas where wood frogs may co-occur with other amphibian species. It was also proven to detect frog DNA as low as 1.83 x 10-3 pg/μL under field conditions. I further demonstrate that the environmental DNA occurrence data can be used to predict wood frog distribution in the Fairbanks North Star Borough with at least moderate predictive accuracy using machine learning algorithms (models predict presence/absence at 59% accuracy using DNA data). The growing use of environmental DNA monitoring will lead to models with even higher accuracy. Lastly, I conduct an environmental DNA mega-transect survey in Alaska and combine the results with citizen science occurrence data from past and present projects to model the distribution of the wood frog across Alaska and the Yukon Territory. Using the same machine learning algorithms, our models correctly predict wood frog presence/absence with 73% accuracy. These results improve upon prior species distribution models developed for wood frogs in Alaska and provide deeper insights into potential wood frog distribution at high latitudes and elevations in Alaska, where anecdotal observations have previously been recorded. Development of the environmental DNA detection assay and interpretation of the species distribution model obtained from alternative lines of evidence provide the means to establish baseline data for wood frogs in Alaska.

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