Citation:

Awkerman, J. AND C. Greenberg. Projected Climate and Hydroregime Variability Constrain Ephemeral Wetland-Dependent Amphibian Populations in Simulations of Southern Toads. Ecologies. MDPI, Basel, Switzerland, 3(2):235-248, (2022). https://doi.org/10.3390/ecologies3020018

Impact/Purpose:

Population-level ecological risk assessment relies on incorporating the appropriate spatial and temporal scale to capture representative environmental and demographic variance.  The reproductive success of amphibians breeding in temporary wetlands is dependent upon variable habitat availability.  This study used climate projections that determine suitable breeding habitat in eight ponds and simulated population dynamics of a common toad species (Anaxyrus terrestris).  Population growth is greatly impacted by long periods without adequate breeding conditions as well as isolation of breeding habitat.    

Description:

Amphibian populations are threatened by multiple potential stressors, including environmental variability and climate-related changes in habitat availability.  Ecological risk assessment of amphibians ideally should encompass the appropriate spatial and temporal scale to adequately capture influential ecological processes and demographic responses.  Determining the population-level impacts of contaminant exposure and pathogens is further complicated in species with biphasic life cycle and both aquatic and terrestrial resource needs.  To demonstrate the importance of representing environmental stochasticity in population assessments, climate change models identifying suitable breeding habitat were used to project population dynamics for southern toad (Anaxyrus terrestris) populations, including three possible effects of habitat availability: 1) complete reproductive failure in years with unsuitable habitat, 2) reduced larval survival as a result of pesticide exposure, and 3) potential immigration of individuals from nearby wetlands with adequate breeding habitat.  Populations were most impacted by long periods of inadequate breeding habitat and isolation from nearby wetlands. The range of projected population abundance in probabilistic approaches underscores the importance of reducing uncertainty in estimated impacts of hydroperiod on reproductive success, and the impact of multiple sequential years of reproductive failure emphasizes the necessity of reliable climate projections to accurately represent the effects of reduced habitat availability on amphibian populations.         

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