Table 3. Local pond variables included in both the linear and piecewise regression models. Only local variables that were present in the last step of a preliminary stepwise model selection procedure (stepAIC; Venables and Ripley 2002) that included all local pond variables as well as distance to Highway 401. We only included two local variables (surface vegetation and proportion of overhanging trees) and distance to the 401 in the stepwise model for the western chorus frog. See methods for explanation. Response Local Variables Species Richness Pond Area, Surface Vegetation Wood Frog Summed Calling Surface Vegetation, Emergent Vegetation Western Chorus Frog Summed Calling Surface Vegetation Spring Peeper Summed Calling pH, Surface Vegetation Leopard Frog Maximum Adults Conductivity, Surface Vegetation American Toad Summed Calling pH Gray Treefrog Summed Calling Pond Area Green Frog Maximum Adults None