Northern Leopard Frogs in North Dakota: Assessing the Conservation Status of a Widespread Amphibian Species
View/ Open
Abstract
North Dakota’s midcontinent location within the Prairie Pothole Region is widely known
for the dense wetlands. These highly productive wetlands are mixed within an agricultural
mosaic which places increased pressure on water quality and overall wetland persistence. These
threats to wetlands affects other, more common species which are presumed to have healthy
populations but lack statewide information. Such is the case with the northern leopard frog
(Lithobates pipiens).
I examined genetic variation for 41 populations across the state. Genetic diversity was
not correlated with latitude, but was negatively correlated with longitude. Along this genetic
diversity gradient, there was a distinctive break near the 100th meridian, a historical boundary
between the arid western United States and the wet eastern side. Further data exploration
revealed wetland densities to be positively correlated with genetic diversity whereas precipitation
and anthropogenic disturbance were not correlated with genetic diversity.
I also examined population genetic structure to identify conservation units. Strong
population structuring was defined by the Missouri River, identifying the Western Badlands and
Western Prairie conservation units. Further structuring of L. pipiens occurred within these two
defined conservation units with rough correspondence to local watersheds. Additionally, I used
approximate Bayesian computational analyses to evaluate coalescence times among the 10
defined units. The Western Prairie and Western Badlands unit shared common ancestry 13,600
to 18,100 generations ago. The coalescence times of the 6 populations within the Western
Prairie unit varied from as recently as 588 generations to 10,900 generations, while populations
within the Western Badlands unit varied as recently as 2,890 generations to 5,220 generations.
In addition to the northern leopard frog genetics research, I conducted research that
considered how sampling biases may lead to inaccurate estimates aquatic invertebrate
abundance. I present an assessment of potential biases associated with sampling a population of
the amphipod Gammarus lacustris in the presence of Polymorphus spp. acanthocephalan
parasites shown to increase positive phototaxis in their amphipod hosts. Results indicated that
the highest captures of G. lacustris individuals were in benthic traps, however, parasitized
individuals were captured most often in surface traps.