Frogs and toads (anurans) are sensitive to a variety of anthropogenic stressors and are widely suggested as indicators of ecological condition. We surveyed 220 coastal wetlands along the U.S. shores of the Laurentian Great Lakes and quantified relationships between presence of anuran species and degree of anthropogenic disturbance. Results were used to derive explicit, functional relationships between environmental condition and anuran occurrences. These functions were subsequently used to calculate a multi-species indicator of ecological condition at other (novel) wetlands. Of 14 anuran species observed, spring peeper (Pseudacris crucifer) exhibited the strongest and most consistent relationship with environmental condition across the entire study area. Other species exhibited significant relationships with the environmental gradient, but the direction of association varied geographically or the overall species abundance was very low (e.g., mink frog, Rana septentrionalis). Even if applied to separate ecological provinces (Laurentian Mixed Forest or Eastern Deciduous Forest), multi-species estimates of wetland condition based on anurans are not much better indicators of environmental condition based on human disturbance than are indices based solely on occurrence of spring peeper. Nevertheless, indicators grounded in explicit relationships with environmental stress are superior to traditional measures (e.g., species richness) that combine species with different responses to the stress gradient. At least one anuran species (spring peeper) can contribute meaningfully to the assessment of ecological condition in Great Lakes coastal wetlands; its value as an indicator will be improved if it can be combined with information from other wetland species such as birds, fishes, and vascular plants.
|Original language||English (US)|
|Number of pages||13|
|Journal||Journal of Great Lakes Research|
|Issue number||SPEC. ISS. 3|
|State||Published - 2007|
Bibliographical noteFunding Information:
This research was supported by a grant from the U.S. EPA’s Science to Achieve Results Estuarine and Great Lakes program through funding to the Great Lakes Environmental Indicators project (U.S. EPA agreement EPA/R-8286750), and a grant from the National Aeronautics and Space Administration (NAG5-11262). Although the research described in this article has been funded in part by the U.S. EPA, it has not been subjected to the agency’s required peer and policy review and therefore does not necessarily reflect the views of the agency, and no official endorsement should be inferred. SJP was also supported by the Zoological Society of Milwaukee, Davidson College biology department, and National Science Foundation grants (DBI-0139153 and DEB-0347326) to Michael E. Dorcas. The Cofrin Center for Biodiversity, University of Wisconsin-Green Bay, and the Natural Resources Research Institute, University of Minnesota Duluth also provided financial, technical, and logistical support. We gratefully acknowledge other scientists involved with the GLEI project, especially V. Brady, T. Brown, J. Brazner, N. Danz, C. Johnson, L. Johnson, T. Hollenhorst, P. Wolter, D. Marks, and the many trained investigators who helped in field surveys. Michael E. Dorcas, Stephen J. Hecnar, and Melinda Knutson provided comments that greatly improved this manuscript. This is contribution number 468 of the Center for Water and the Environment, Natural Resources Research Institute, University of Minnesota Duluth.
- Biological indicator
- Coastal wetlands
- Ecological condition
- Great Lakes