Response of Amphibian and Invertebrate Communities to Wetland Mitigation in the Greater Yellowstone Ecosystem

Wetlands play a critical role in supporting freshwater biodiversity and ecosystem services, but human activities have resulted in large-scale loss and degradation of these habitats across the globe. To offset the decline of wetland area, mitigation wetlands are now frequently constructed, but their ability to replace the functions of natural habitats, including providing habitat for native fauna, remains uncertain. A recent highway reconstruction project in northwestern Wyoming caused impacts to and the destruction of multiple natural wetlands. To mitigate this loss, new wetlands were constructed along the highway corridor. To evaluate the performance of these created wetlands relative to reference (not affected by road construction activities) and impacted wetlands (impacted but not destroyed by road construction), I measured habitat variables, sampled aquatic invertebrates, and conducted repeated counts of amphibian larvae and Columbia spotted frog egg masses. My findings indicate that taxonomic richness of macroinvertebrates was lower in created wetlands than impacted or reference wetlands, with similar richness in impacted and reference wetlands. Age of constructed wetlands was positively correlated with taxonomic richness of invertebrates, but no relationship existed between richness and wetland isolation. The most important environmental variable related to macroinvertebrate richness was percent cover of aquatic vegetation, with the number of taxa positively correlated with vegetation cover. Community composition of invertebrates in created wetlands differed from that in reference and impacted sites, with created wetlands lacking some passive dispersers. Amphibians exhibited species-specific responses to wetland creation, with tiger salamander, boreal toad, and boreal chorus frog larvae occurring at higher densities in created wetlands than reference and impacted wetlands. Columbia spotted frogs exhibited the opposite response, occurring at higher densities in reference and impacted wetlands than created wetlands. Early drying of created wetlands resulted in catastrophic reproductive failure on several occasions, potentially resulting in an ecological trap or population sink for amphibians. Impacted wetlands were similar to reference wetlands in habitat characteristics, invertebrate, and amphibian communities, highlighting the resiliency of natural wetlands to minor disturbance. Managers with the goal of benefiting native wildlife species should take into account the life history requirements (e.g. minimum hydroperiod) of all target species when creating and restoring wetlands