Species interactions and the effects of climate variability on a wetland amphibian metacommunity
We examined how populations of three species of wetland-breeding amphibians, which varied in life history requirements, responded to a six-year period of extremely variable precipitation.
This interval was punctuated by both extensive drought and heavy precipitation and flooding, providing a natural experiment to measure community responses to environmental perturbations.
From 2010 to 2011, an extreme drying event occurred at SMNWR, with low rainfall leading to reduced hydroperiod or drying of wetlands that typically hold water year-round.
Then, in 2012, Tropical Storm Debby impacted the Florida panhandle, completely flooding many wetlands throughout SMNWR, leading to changes in hydroperiod and colonization of previously isolated wetlands by fishes. An additional flood in 2013 maintained high fish colonization.
From 2010 to 2011, an extreme drying event occurred at SMNWR, with low rainfall leading to reduced hydroperiod or drying of wetlands that typically hold water year-round.
Then, in 2012, Tropical Storm Debby impacted the Florida panhandle, completely flooding many wetlands throughout SMNWR, leading to changes in hydroperiod and colonization of previously isolated wetlands by fishes. An additional flood in 2013 maintained high fish colonization.
We estimated occurrence dynamics using a discrete hidden Markov modeling approach that incorporated information regarding habitat state and predator–prey interactions. This approach allowed us to measure how metapopulation dynamics of each amphibian species was affected by interactions among weather, wetland hydroperiod, and co-occurrence with fish predators.
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Rather than a consistent response across species (e.g., more water leads to more wetland breeding amphibians that rely on water), we found that responses to changes in water availability varied among species. These differences likely emerge because of species-specific traits that affect how populations respond to changes in hydrology and predation pressure. These interactions with habitat and predators are the key determinant as to whether climatic variability affects the occurrence of each species.
Sensitivity analyses for occupancy of (a) ornate chorus frog, (b) mole salamander, (c) pig frog, and (d) fishes. Ornate chorus frog occupancy was most sensitive to changes in habitat drying (1 − η Habitat) and the removal of fishes (1 − ϕ Fish) from long-duration wetlands. Mole salamander occupancy was most sensitive to the removal of fishes from long-duration wetlands, while pig frog occupancy was relatively insensitive to changes in fish occurrence.
Dynamic models can be powerful tools for disentangling the processes that lead to changes in species distributions. Characterizing the underlying colonization and extinction processes that determine metacommunity dynamics can provide key insights into how changes in environmental and climatic variability are likely to impact amphibian occurrence on the landscape. By capturing such changes over time, we were able to understand the processes that shape amphibian occurrence in this coastal wetland system.