Over the hills and through the farms: Land use and topography influence genetic connectivity of northern leopard frog (Rana pipiens) in the Prairie Pothole Region

Context Agricultural land-use conversion has fragmented prairie wetland
habitats in the Prairie Pothole Region (PPR), an area with one of the most
wetland-dense regions in the world. This fragmentation can lead to
negative consequences for wetland obligate organisms, heightening risk of
local extinction and reducing evolutionary potential for populations to
adapt to changing environments. Objectives This study models biotic
connectivity of prairie-pothole wetlands using landscape genetic analyses
of the northern leopard frog (Rana pipiens) to: (1) identify population
structure and (2) determine landscape factors driving genetic
differentiation and possibly leading to population fragmentation. Methods
Frogs from 22 sites in the James River and Lake Oahe river basins in North
Dakota were genotyped using Best-RAD sequencing at 2868 bi-allelic single
nucleotide polymorphisms (SNPs). Population structure was assessed using
STRUCTURE, DAPC, and fineSTRUCTURE. Circuitscape was used to model
resistance values for ten landscape variables that could affect habitat
connectivity. Results STRUCTURE results suggested a panmictic population,
but other more sensitive clustering methods identified six spatially
organized clusters. Circuit theory-based landscape resistance analysis
suggested land use, including cultivated crop agriculture, and topography
were the primary influences on genetic differentiation. Conclusions While
the R. pipiens populations appear to have high gene flow, we found a
difference in the patterns of connectivity between the eastern portion of
our study area which was dominated by cultivated crop agriculture, versus
the western portion where topographic roughness played a greater role.
This information can help identify amphibian dispersal corridors and
prioritize lands for conservation or restoration.