USDA Forest Service

Pacific Southwest Research Station
Pacific Southwest
Research Station

800 Buchanan Street
Albany, CA 94710-0011
(510) 883-8830
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Research Topics Ecosystem Processes

Sierra Nevada Ecosystems

Multi-scale environmental relationships and population status of lentic-associated amphibians in the Lake Tahoe basin

The Research

This project focuses on analysis of distribution, habitat associations, and genetic data for at-risk amphibian species in the Lake Tahoe Basin, with the goal of developing conservation and restoration recommendations. It is a collaborative study among six institutions: three research institutions including USFS Pacific Southwest Research Station’s Sierra Nevada Research Center, University of California, Davis, and University of Nevada, Reno; and three resource management agencies including USDAFS Lake Tahoe Basin Management Unit, Nevada Division of State Lands, and Tahoe Regional Planning Agency.

Aquatic ecosystems support a significant proportion of the biological diversity in the Lake Tahoe basin, and lentic ecosystems support the majority of vertebrate species and individuals associated with aquatic ecosystems in the basin. Restoration of terrestrial and aquatic ecosystems in the Lake Tahoe basin is a high regional and national priority. President Clinton’s visit to the basin in 1997 precipitated a scientific assessment, which indicated that lentic ecosystems in the Lake Tahoe basin have been degraded, and the topographically confined Lake Tahoe basin may put population persistence at greater risk. Amphibians are restricted to breeding in water, thus they are predisposed toward spatial metapopulation structures, particularly those that breed in lentic habitats. A metapopulation is a population that is spatially structured into assemblages of local breeding populations and migration among local populations affects local dynamics such as occupancy, extinction and recolonization. The effect of population size on extinction is non-linear, with small populations having exponentially greater probability of extinction as a result of deterministic processes (e.g., Allee effect) or stochastic events. The potential peril of existing amphibian populations, degraded habitat conditions, and short-term opportunities for restoration afforded by the Lake Tahoe Restoration Act (2000) emphasize the urgent need to investigate questions of population persistence and its driving factors.

This project combines and builds on data from recent distributional surveys, environmental assessments, and genetic variation/structure, to develop habitat associations models and assess population status and risk factors for two at-risk species (long-toed salamander [Ambystoma macrodactylum] and western toad [Bufo boreas]) and one more common species (Pacific treefrog [Pseudacris regilla]).


1. Develop multi-scale models of environmental/habitat associations for all three focal amphibian species.

2. Describe population genetic structure for long-toed salamander and western toad.

3. Infer demographic status for long-toed salamanders and western toads to inform management priorities and directions for amphibians in the Lake Tahoe basin.

4. Evaluate landscape features and land management influences relative to genetic structure, habitat conditions, and other relevant environmental variables in the Lake Tahoe basin to generate predictive models of long-toed salamander and western toad population size, structure, migration, and gene flow.

5. Develop management recommendations and restoration priorities all three focal amphibian species.

Methods and Design

The overall design of this study requires the integration of species-specific multi-scale environmental models with information on genetic variation and structure. Multi-scale environmental/habitat models for species occupancy and abundance are being built using a combination of field data and local and landscape characteristics surrounding each lentic site (derived using geographical information systems [G.I.S.]). Key features being explored as predictors of species distribution and abundance include: topographic features, lake/meadow substrates and aquatic vegetation, surrounding terrestrial vegetation, recent precipitation patterns, proximity to other lentic sites, and occurrence of exotic predatory fish. Multiple environmental models of focal species occupancy and abundance are being developed to address both ecological and management-based questions. The use of multiple models is expected to provide more detailed insights into habitat relationships and options for land management and monitoring.

For genetic analyses, tissue samples were collected from locations spanning the range of the extant populations of long-toed salamanders and western toads within the Lake Tahoe basin and from several populations outside of the basin (for context). Microsatellite genetic markers are being used to discern genetic variation and structure within the basin and to determine if the basin represents a unique genetic unit. The influences of watershed topography and overall distance on gene flow are being examined using standard genetic analysis methods and software.

Application of Research Results

Final environmental models will be combined with information on factors affecting genetic structure and gene flow to infer demographic status and identify the most at-risk populations of long-toed salamander and western toads. This information can then be used in land management, conservation and restoration planning in the basin.


Survey and GIS data were collected in the Lake Tahoe basin of California and Nevada . The basin has 63 major watersheds that contain over 330 lakes, 3 marshes, 2 fens, and hundreds of acres of meadow, of which an unknown number are perennially wet.

Lead Scientists/Collaborators

1) Manley, P.M. and Lind, A.J.; 2) Roth, J.; 3) Savage, W.S. and Shaffer, H.B.; 4) Peacock, M.

1) USDA Forest Service, PSW Research Station
Sierra Nevada Research Center
2121 Second Street, Suite A-101
Davis, CA 95528
ph: 530-759-1702
fax: 530-747-0241

2) USDA Forest Service, Lake Tahoe Basin Management Unit

35 College Drive 
S. Lake Tahoe, CA 96150

3) Department of Evolution and Ecology
University of California, Davis, CA

4) Biology Department, University of Nevada, Reno, NV

Publications and Products

Manley, P.N. and A.J. Lind 2005. Status and change of amphibian and reptile populations and habitat conditions in lentic ecosystems in the Lake Tahoe basin. Report submitted to: USFS Lake Tahoe Basin Management Unit, Tahoe Regional Planning Agency, and Nevada Division of State Lands. 65pp (August).

Peacock, M.M. and V. Kirchoff. 2005. Genetic analyses of Bufo boreas populations in the Lake Tahoe basin. Final Report submitted to USDA Forest Service, Lake Tahoe Basin Management Unit, South Lake Tahoe, California (October). 57pp.

Savage, W.K. and H.B. Shaffer 2006. Spatial population genetic structure of the southern long-toed salamander (Ambystoma macrodactylum) in the Lake Tahoe Basin Management Unit. Final Report submitted to USDA Forest Service, Lake Tahoe Basin Management Unit, South Lake Tahoe, California (March). 52pp.

Last Modified: Aug 29, 2016 10:56:19 AM