Modeling apple snail population dynamics on the Everglades landscape
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The Florida Everglades has diminished in size and its existing wetland hydrology has been altered. The endangered snail kite (Rostrhamus sociabilis) has nearly abandoned the Everglades, and its prey, the apple snail (Pomacea paludosa), has declined.
We developed a population model (EverSnail) to understand apple snail response to inter- and intra-annual fluctuations in water depths over the Everglades landscape. EverSnail was developed as a tool to understand how apple snails respond to different hydrologic scenarios.
EverSnail is an age- and size-structured, spatially-explicit landscape model of P. paludosa in the Everglades. Landscape-level inputs are water depth and air temperature. We conducted sensitivity analyses by running EverSnail with ±20 % the baseline value of eight parameters.
EverSnail was sensitive to changes in survival and water depth associated with reproduction. The EverSnail population varied with changes and/or differences in depth generally consistent with empirical data; site-specific comparisons to field data proved less reliable. A simulated 3-year wet period resulted in a shift in apple snail distribution, but little change in total abundance over the landscape. In contrast, a simulated 3-year succession of relatively dry years resulted in overall lower snail abundances.
Comparisons of model output to empirical data indicate the need for more data to better understand, and eventually parameterize, several aspects of snail ecology in support of EverSnail. A primary value of EverSnail is its capacity to describe the relative response of snail abundance to alternative hydrologic scenarios considered for Everglades water management and restoration.
KeywordsPomacea paludosa Population matrix model Distribution Abundance Florida Wetlands Hydrology Management Restoration Snail kite
We appreciate the support of Ronnie Best (USGS, retired) and Craig Conzelmann (USGS) in facilitating the collaboration for this effort. We thank Alicia LoGalbo (National Park Service, Everglades), Rena Borkhataria (University of Florida), and Wingrove Duverney (USGS contractor) for their input into the formulation of this model. Pam Telis (US Army Corps of Engineers) provided helpful information regarding the use of EDEN water depth data. Bethany Wight (University of West Florida) provided technical assistance regarding site-specific hydrologic and snail density data. David Bucklin (University of Florida) created the Figure-1 map. We appreciate the comments from three anonymous reviewers and James Beerens (USGS) on drafts of this manuscript. Funding from the USGS National Climate Change and Wildlife Science Center project “La Florida: A Land of Flowers on a Latitude of Deserts” provided some support for DLD. SSR and DLD were supported by the USGS’s Greater Everglades Priority Ecosystem Science program. Views expressed here do not necessarily represent the views of the U.S. Fish and Wildlife Service. Any use of trade, product, or firm names in this article is for descriptive purposes only and does not imply endorsement by the U.S. Government.
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