Landscape level influences on pond-breeding amphibian diversity in Minnesota's three ecoregions

Background/Question/Methods

 Habitat loss, fragmentation, and isolation pose significant threats to pond-breeding amphibians.  Anthropogenic influences that contribute to these factors are particularly harmful because the majority of amphibians require two vastly different habitats for completion of their life cycle.  We investigated how pond-breeding amphibians respond to landscape configuration and composition across Minnesota’s three major ecoregions.  This study addresses several important questions including how the number of wetlands, wetland area, and land use within 1000m of wetland breeding sites impact species richness and whether that differs between ecoregions.  We summarized data collected from the North American Amphibian Monitoring Program (NAAMP) and used GIS to extract and compile landscape data for NAAMP routes across Minnesota’s three ecoregions.  We tested hypotheses to determine whether there was differences between Minnesota’s three ecoregions in how amphibians respond to landscape factors that represent disturbances (e.g. roads, developed land, and agriculture) or habitat (e.g. wetlands and forests).  We might expect that pond-breeding amphibians will have lower species richness in areas with higher proportions of landscape modifications (disturbances) because these disturbances would increase the likelihood of extinction of individual populations.

Results/Conclusions

We found that the number of wetlands near a survey site was more influential in Eastern Deciduous and Northern Coniferous Forests than in the Great Plains, but having multiple wetland types near a survey site was more influential in the Northern Coniferous Forest than the other two ecoregions. Generally, landscape variables connected to anthropogenic influences (e.g., roads, developed land or row crops) were negatively associated with species richness, and landscape variables indicating more habitat availability (e.g., wetland area) were positively associated with species richness.  Interestingly, trends in species richness indicate differences in response to proportion of land cover in different agricultural uses - and these differences were not consistent among the three ecoregions.  Our results indicate that amphibian species richness may be impacted by multiple influences at the landscape level across Minnesota’s three ecoregions, and additional studies at multiple scales are needed to evaluate the importance of landscape features for presence of individual species and community dynamics.