Projected Climate and Hydroregime Variability Constrain Ephemeral Wetland-Dependent Amphibian Populations in Simulations of Southern Toads

  • Authors: Awkerman, Jill A.; Greenberg, Cathryn H.
  • Publication Year: 2022
  • Publication Series: Scientific Journal (JRNL)
  • Source: Ecologies
  • DOI: 10.3390/ecologies3020018


Amphibian populations are threatened globally by stressors, including diminishing availability
of suitable wetland breeding sites, altered hydroregimes driven by changing weather patterns,
and exposure to contaminants. Ecological risk assessment should encompass spatial and temporal
scales that capture influential ecological processes and demographic responses. Following the
PopGUIDE framework of population model development for risk assessment, we used matrix population
models, in conjunction with existing hydroregime predictions, under a climate change scenario
to evaluate the effects of environmental stochasticity and aquatic pesticide exposure on amphibians
that are dependent on ephemeral wetlands. Using southern toads (Anaxyrus terrestris) as an example,
we simulated population dynamics with breeding success dependent on hydroregime suitability.
Years were defined as optimal, marginal, or insufficient for successful toad recruitment, based on the
duration of their potential breeding season and rate of larval development to metamorphosis. We
simulated both probabilistic and chronologically specific population projections, including variable
annual fecundity, based on hydroregime suitability and reduced larval survival from carbaryl exposure.
In our simulations, populations were more negatively impacted by prolonged drought, and
consequently multiple sequential years of reproductive failure, than by aquatic pesticide exposure.
These results highlight the necessity of reliable climate projections to accurately represent the effects
of altered hydroregimes on amphibian populations. Risk assessment approaches could be improved
with flexible modifications that allow inclusion of various extrinsic stressors and identification of
demographic and ecological vulnerabilities when precise data are lacking.

  • Citation: Awkerman, Jill A.; Greenberg, Cathryn H. 2022. Projected Climate and Hydroregime Variability Constrain Ephemeral Wetland-Dependent Amphibian Populations in Simulations of Southern Toads. Ecologies. 3(2): 235-248.
  • Keywords: amphibian, climate, pesticide, hydroregime, ephemeral wetland, population model, risk assessment, southern toad
  • Posted Date: August 17, 2022
  • Modified Date: August 17, 2022
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