What was once thought to be a highly abundant amphibian throughout much of North America, the northern leopard frog (Rana pipiens) has been recently petitioned for federal protection. Research and monitoring programs indicate widespread population declines and the U.S. Fish & Wildlife Service is currently seeking species information, particularly on genetic health. The northern leopard frog is unique compared to other amphibians in North Dakota in the fact that it behaviorally evades harsh winter weather by over-wintering in available wetlands at the water/mud interface. However, this over-wintering strategy can be deadly if freezing temperatures (i.e., ice) extend to the wetland bottom. Therefore, northern leopard frogs require wetlands with deep water, to survive winter. However, during severe drought events in North Dakota, such drought refugia become uncommon. Thus, the spatial and temporal distribution of drought refugia can play an important role in the distribution of northern leopard frogs on the landscape. Accordingly, understanding where populations persist during past climate extremes can be used to provide insights into the role of drought refugia in northern leopard frog population dynamics, particularly in terms of genetic diversity and gene flow across the landscape.

Objectives:

The study I propose is designed to develop a landscape genetics model by integrating genetic surveys of populations occurring at known long-term overwintering sites with environmental and landscape variables. This work will involve three objectives:

1. Examine population genetic structures at drought refugia sites to understand genetic sources for potential re-colonization of northern leopard frog populations in ND
2. Develop landscape genetic models to evaluate current influences of gene flow on northern leopard frog populations in ND

Progress:

To date, I have completed my first year's field sampling in which I obtained 40 northern leopard frog populations throughout North Dakota. I have successfully optimized 8 previously developed microsatellite markers and have run these markers on a total of 18 populations. Currently, I am in the process of optimizing additional microsatellite markers as well as analyzing genotyping results.

Significance:

My proposed research is very timely due to the recent proposed listing of the northern leopard frog. Managers are seeking genetic data to help identify regions/populations that should be included in the listing. By incorporating GIS models, I will be able to predict how geographic and environmental variables influence the spatial and temporal distribution of northern leopard frog populations. For instance, limited genetic variability and high structure is expected for isolated populations found in regions where distinctly separate overwintering wetlands occur, such as the southwestern part of the state. This research extends standard landscape genetic models to incorporate important spatial and temporal distribution of drought refugia sites to produce more robust models needed to understand long-term population structure of northern leopard frogs. This research will contribute valuable insights for state and federal managers as they consider the petition for listing the northern leopard frog under the Endangered Species Act.

Research Outcomes:

     Fisher, J., K. Purcell and C. Stockwell. Initial Survey of the Genetic Diversity of Northern Leopard Frog Populations in North Dakota. North Dakota Chapter of the Wildlife Society Annual Meeting, Mandan, ND, 02/2011.

     Fisher, J., K. Purcell and C. Stockwell. Survey of the Genetic Diversity of Northern Leopard Frog Populations in North Dakota. 2011 Joint Meeting of Ichthyologists and Herpetologists. July 8, 2011 (Presentation Accepted).