projects > across trophic level system simulation (atlss) - alligators
Across Trophic Level System Simulation (ATLSS) - Alligators
The American Alligator (Alligator mississippiensis) is a keystone species of the South Florida Ecosystem. Population growth and survival depends directly on the hydrologic functioning of South Florida watersheds. Each of these watersheds has experienced, and continues to experience, substantial degradation. In fact, over half of the wetlands within central and southern Florida have been lost during the past century and those that remain have been highly fragmented and severely degraded (Weaver et al., 1994). Currently, planning is underway for what may become the largest ecosystem restoration ever undertaken. Although other endangered and keystone species occur within the ecosystem, the American Alligator's role as a top predator and its effect on the structuring of plant communities and associated aquatic animals (Mazzotti and Brandt, 1994) make it an ideal indicator of ecosystem health. The response of alligator populations to spatio-temporal changes in hydrological conditions throughout the South Florida Ecosystem are integral to the evaluation of any restoration alternative.
The ATLSS American Alligator Production Index (API) Model was developed as a coarse indicator of the yearly production potential (probability of producing nests and offspring successfully) for the American Alligator in South Florida based upon local habitat and hydrologic conditions. The production potential of this species is directly influenced by unique environmental conditions occurring throughout its range in Florida. The API model addresses only the effects of relative local habitat quality and hydrological dynamics. Consequently, this model should not be interpreted as providing estimates of population dynamics or viability. Further, the temporal extent of the model is not likely to encompass long-term changes in habitat quality. Particularly, stabilized hydrologic regimes may result in slow degradation or improvement of habitat not included in this model. Little verification of the model's performance was possible except for those populations in Everglades National Park and Water Conservation Areas 2 and 3. In addition, the density of essential landscape features (e.g., tree islands) within Water Conservation Area 1 (ARM Loxahatchee National Wildlife Refuge) are "best guess" approximations since the data are currently lacking.
U.S. Department of the Interior, U.S. Geological Survey
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