Evaluating the Ecological Importance of Seasonal Marshes as Breeding Habitats for Native Amphibians

Seasonal marshes, which fill in during wet seasons and are dry during part of the year, are important breeding grounds for many native amphibians. They are not as well protected as permanent water bodies because of their small size, variable water regime, and for the many of them not being inventoried by wetland lists. The present study examines the ecological value of seasonal wetlands as breeding habitat for amphibians using a well-structured narrative synthesis of 12 peer-reviewed studies that investigated the importance of temporary wetlands, pond-breeding amphibians and wetland connectivity. Evidence was grouped into six habitat dimensions: hydroperiod, pond area, predator regime, pond clustering and connectivity, surrounding terrestrial habitat and species interactions. The synthesis demonstrates that hydroperiod is the key factor regulating breeding success: drying occurs before metamorphosis leads to reproductive failure, while permanent water brings in fish which exclude sensitive species. Larval density and richness were greatest in fishless wetlands of intermediate size, while the number of neighbouring ponds and the amount of nearby forest affected colonisation and extinction and larval density. The number of species was found to vary for different combinations of habitat traits so that a variety of hydroperiods within a landscape will result in a higher diversity of amphibians than a single wetland type. Replacements often did not achieve amphibian goals, and the reduction in hydroperiods due to climate change became a problem. Two summary tables are provided to relate habitat attributes to amphibian responses and conservation challenges with management responses. Findings support protection of wetland networks, rather than individual sites, and hydroperiod diverse management and monitoring of wetlands with multiple metrics over time. The evidence is mainly limited to the temperate North America and therefore needs to be localized prior to extrapolation to monsoonal and tropical seasonal marshes.