Document Type

Dissertation

Degree

Doctor of Philosophy (PhD)

Major/Program

Biology

First Advisor's Name

Alessandro Catenazzi

First Advisor's Committee Title

Committee Chair

Second Advisor's Name

Elizabeth Anderson

Second Advisor's Committee Title

Committee Member

Third Advisor's Name

Christopher Baraloto

Third Advisor's Committee Title

Committee Member

Fourth Advisor's Name

Heather Bracken-Grissom

Fourth Advisor's Committee Title

Committee Member

Fifth Advisor's Name

Maureen Donnelly

Fifth Advisor's Committee Title

Committee Member

Keywords

Amphibian, Batrachochytrium, Population, Disease, Genetics, Recovery, Costa Rica, Community, chytrid

Date of Defense

10-23-2020

Abstract

The Anthropocene epoch has been marred by a global biodiversity crisis and the advent of Earth’s sixth mass extinction. Amphibians, the most threatened vertebrate taxa, have become the poster children for this sixth mass extinction. The pathogenic fungus Batrachochytrium dendrobatidis has been blamed for many of declines and extinctions seen in amphibians. The now panglobal Bd causes the disease chytridiomycosis in a large number of amphibian species and has been linked to population crashes in Central and South America, Australia, Europe, and the United States. Now enzootic around the world, amphibian populations continue to confront Bd in a long-term battle between host and pathogen. The toll exacted by the panzootic spread of Bd was clear, but the persistence of this lethal pathogen in habitats with susceptible species is still poorly understood. Herein I examined the response of amphibians in the Neotropics to this new, enzootic stage of Bd presence. I reviewed the current state of amphibian populations in Costa Rica, one of the first countries to report mass amphibian declines, and discussed recent report of species rediscoveries and population recoveries. In the Andes of southern Peru I identified a competent disease reservoir, the gladiator frog Boana gladiator, that appears to be driving terrestrial and aquatic transmission of Bd and potentially mediating the amphibian community structure as a result. While B. gladiator may hamper other species from rebounding, in Costa Rica I assessed a reportedly recovering population of another stream-breeding hylid, Duellmanohyla rufioculis. I determined that the Rara Avis population of D. rufioculis appears to have recovered from near undetectability and remains stable, or even increasing, despite the continued presence of Bd in the population and community. I found that the genetic structure of this population shows telltale signs of a major demographic bottleneck and of recent expansion, corroborating the field findings that the population has recently expanded. The data collected during my dissertation on the long-term dynamics of disease transmission, amphibian population dynamics, and the genetic consequences of declines and recovery provide vital clues on how populations can persist with an ever-present pathogen.

Identifier

FIDC009207

ORCID

https://orcid.org/0000-0003-0623-0969

Available for download on Saturday, October 15, 2022

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