PhD Dissertation Defense - Geography and Geoinformation Science

PhD Candidate: Carrie Lewis

PhD of Science, Earth Systems and Geoinformation Sciences

Department of Geography and Geoinformation Science 

Title: Using Species Distribution Models to Identify Refugia for Harlequin Frogs (Atelopus) in Panama

Dissertation Chair:  Dr. Paul Houser (GMU, GGS)

Committee Members:

Dr. Arie Croitoru (GMU, CDS)

Dr. Donglian Sun (GMU, GGS)

Dr. Brian Gratwicke (Smithsonian National Zoo and Conservation Biology Institute)

Abstract:

The disease chytridiomycosis, caused by the fungus Batrachochytrium dendrobatidis (Bd), is driving global amphibian decline, and Harlequin frogs in the genus Atelopus are among the most threatened amphibians. There are seven species of Atelopus that are native to Panama, and all are critically endangered or extinct, though five species are present in ex situ captive assurance colonies. Captive breeding is a temporary solution with the goal of reintroduction in the wild, yet Bd is still present in Panama and there are no methods to remove it from the environment. It is hypothesized that species distribution models (SDMs) could be used to identify areas of environmental refugia with low suitability for Bd where amphibians may be able to persist in the presence of the fungus. These locations could support relict amphibian populations or be used for reintroduction efforts.

We used SDMs of Atelopus and Bd in Panama to explore this hypothesis and to identify potential areas for reintroduction. We built an SDM of Atelopus habitat suitability using climate data and historic Atelopus locations. We created our own high-resolution remotely sensed environmental dataset of daily meteorological values and used high-quality presence/absence survey data to build new Bd SDMs. We tested various time scales to evaluate how weather prior to testing affected Bd presence and intensity. We found that 15 days prior to sampling, inclusive of sampling date, was the most predictive time scale for Bd suitability. We also found that reasonable Bd SDMs can be built using infection intensity as well as basic presence/absence. We generated daily predictive maps of the probability of Bd occurrence in Panama from 2005-2018 and averaged them by season. Higher Bd suitability tended to be found at higher elevations, a pattern found in previous Bd studies.

We created seasonal threshold Bd suitability maps and used a new dataset of relict Atelopus locations to examine the Bd suitability for those sites. For many sites, the models predicted that 1/3 or fewer of the seasons were suitable, suggesting that such sites may be appropriate for reintroduction. However, some relict Atelopusvarius sites had very high suitability, indicating that these populations may be persisting with Bd. With this information on relict populations, we presented a methodology using seasonal Bd suitability and probability of Bd occurrence to identify locations in Panama that are mostly unsuitable or trending unsuitable for Bd. These areas may act as refugia that could support relict Atelopus populations or reintroduction efforts.

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Meeting ID: 995 2255 9313

Passcode: 182254

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