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projects > use of amphibian communities as indicators of restoration success > work plan
Project Work Plan
U.S. Geological Survey, Greater Everglades Priority Ecosystems Science (GE PES)
Fiscal Year 2005 Study Work Plan
Project Title: Use of Amphibian Communities as Indicators of Restoration Success
Project Start Date: 2004 Project
End Date: 2006 (per discussion with Ronnie Best)
Web
Site: sofia.usgs.gov
Location
(Subregions, Counties, Park or Refuge): Total System
Funding
Source: USGS Greater Everglades Priority Ecosystems Science (GE PES) (this task is funded under
Don DeAngelis ATLSS' program)
Other
Complementary Funding Source(s): CESI: Effects of Public Land Use on Threatened, Endangered, and
Indicator Species funded the initial work on this study through 2003.
Principal
Investigator(s): Kenneth G. Rice, Frank J. Mazzotti
Project
Personnel: Amanda Rice
Supporting
Organizations: University of Florida
Associated/Linked
Projects: CESI: Effects of Public Land Use on Threatened, Endangered, and
Indicator Species
Overview
& Objective(s): Declines in amphibian populations have
been documented by scientists worldwide from many regions and habitat
types. No single cause for
declines has been demonstrated, but stressors like acid precipitation,
environmental contaminants, the introduction of exotic predators, disease agents,
parasites, and the effects of ultraviolet radiation have all been
suggested. Because of their
susceptibility to these and other stressors, amphibians are important as
indicators of ecosystem health.
Amphibians are present in all habitats and under all hydrologic regimes
in the Everglades. The species
present and the occupancy rate of a given species differ greatly across those
gradients. These differences are
due to hydropattern, vegetation, and other environmental factors. The combination of species composition
and proportion of each habitat occupied at a given time form unique communities
defined by those environmental factors.
Therefore, if these communities can be reliably defined and measured,
Everglades restoration success can be evaluated, restoration targets can be
established, and restoration alternatives can be compared. This study will develop methodologies
for defining and measuring the membership and area occupancy of amphibian
communities. Further, we will
investigate the relationship of occupancy of amphibians with hydroperiod and
other environmental factors.
Finally, we will provide a method for measuring restoration success
based on these communities. Our
objectives include:
- Define amphibian communities appropriate for
evaluating restoration success.
- Develop methods for measuring the area occupancy
of amphibian communities across habitats and environmental gradients.
- Investigate the relationship of occupancy with
hydroperiod and other environmental factors.
- Develop restoration targets for the amphibian
community of the Greater Everglades.
- Develop a restoration tool for amphibian
communities that measures restoration success and also compares
restoration alternatives.
- Develop an index of biological integrity for
amphibians that provides a framework for scientifically defensible
decisions by restoration managers.
Specific Relevance to Major
Unanswered Questions and Information Needs Identified: (Page numbers below refer to DOI Science Plan.)
- This study addresses
questions identified in DOI's Science Plan in Support of Ecosystem Restoration,
Preservation, and Protection in South Florida (DOI's Everglades Science Plan)
including:
- Monitoring of ecological
responses of amphibians to hydrologic change was specifically listed as a
science need in the Southern Golden Gate Estates Hydrologic Restoration Project
as well as the need for amphibian larval sampling.
- The study supports the
Arthur R. Marshall Loxahatchee NWR Internal Canal Structures project as it (1)
provides monitoring and assessment of responses of aquatic communities and
habitats (p. 37) and (2) helps understand the ecological effects of hydrology
and water quality on refuge resources (p. 40).
- The study support the
Southwest Florida Feasibility Study Project by providing modeling to predict
species-level responses to habitat change (p. 50) and monitoring of key indicators
(p. 51).
- The need for monitoring
and modeling of ecological communities and indicator species is specifically
mentioned in the Florida Bay and Florida Keys Feasibility Study (p. 78), Ten
Mile Creek Reservoir Assisted Stormwater Treatment Area Project (p. 34),
Henderson Creek/ Belle Meade Restoration Project (p. 56), Southwest Florida
Feasibility Study (p. 52), Florida Bay and Florida Keys Feasibility Study (p. 76), Landscape-Scale Modeling (p. 81), and Everglades National Park Fire
Ecology Science Action Plan (p. 125).
- This project addresses
several science objectives in the USGS Science Plan in Support of Everglades
Restoration. Primarily, this work
is concentrated under Goal 2B "Restore, Preserve, and Protect Natural Habitats
and Species - Ecological Indicators." The tasks directly address 4 of the 5 science objectives:
- We examine the effects
of hydropattern and develop information required for restoration targets
(2B-SG1).
- We began a monitoring
program to establish baselines and examine the current state of Everglades
amphibian communities (2B-SG3).
- We have developed a
monitoring program for amphibian communities throughout the Everglades for use
in evaluation of restoration success (2B-SG4).
- We are developing models
as tools for predicting the effects of restoration alternatives and determining
restoration success (2B-SG5).
Status: We
continue to use data previously collected from Everglades National Park to
develop methods for defining amphibian communities using the Proportion Area
Occupied (PAO) model and multivariate statistical techniques (see Fact Sheet 2004-3106). In Everglades
National Park and adjacent Water Conservation Areas 3A and 3B, we have begun a
large scale study to determine the PAO by each amphibian species across
habitats defined by hydropattern. The PAO method estimates the abundance of
sites at which each species occurs based on the capture results of several
visits to each site. This method takes into account that some species are more
difficult to detect, given that they are present, than others. This sampling is
done along a hydrologic gradient from very long hydroperiod sloughs to the
extremely short hydroperiod rocky glades of eastern Everglades National Park.
We have initiated sampling including call count, visual encounter surveys, PVC
refugia captures, and trapping in over 20 sites.
Recent Products: We have completed Fact Sheet 2004-3106 and have
presented our initial findings and models to national and international
conferences (presentations and posters).
Planned Products: We are presenting the results of this work at the
NCER conference in December. We plan to complete peer-reviewed manuscripts on
the study upon completion and provide the monitoring program and simulation
models to CERP managers.
WORK PLAN
Title of Task 1: Use of Amphibian
Communities as Indicators of Restoration Success
Task Funding: USGS Greater Everglades Priority Ecosystems Science (GE PES)
Task
Leaders: Kenneth G. Rice, USGS; Frank J. Mazzotti, University of Florida
Phone: 954-577-6305
FAX:
954-577-6347
Task Status (proposed or active): Active
Task
priority: High
Time Frame for Task 1: 2004-2006
Task
Personnel: Amanda Rice, University of Florida
Task Summary and
Objectives: Declines
in amphibian populations have been documented by scientists worldwide from many
regions and habitat types. No
single cause for declines has been demonstrated, but stressors like acid
precipitation, environmental contaminants, the introduction of exotic
predators, disease agents, parasites, and the effects of ultraviolet radiation
have all been suggested. Because
of their susceptibility to these and other stressors, amphibians are important
as indicators of ecosystem health.
Amphibians are present in all habitats and under all hydrologic regimes
in the Everglades. The species
present and the occupancy rate of a given species differ greatly across those
gradients. These differences are
due to hydropattern, vegetation, and other environmental factors. The combination of species composition
and proportion of each habitat occupied at a given time form unique communities
defined by those environmental factors.
Therefore, if these communities can be reliably defined and measured,
Everglades restoration success can be evaluated, restoration targets can be
established, and restoration alternatives can be compared. This study will develop methodologies
for defining and measuring the membership and area occupancy of amphibian
communities. Further, we will
investigate the relationship of occupancy of amphibians with hydroperiod and
other environmental factors.
Finally, we will provide a method for measuring restoration success
based on these communities. The
importance of amphibian communities to Everglades restoration has been
recognized and listed as critical priority research needs (see USGS Ecological
Modeling Workshop and the DOI Science Plan in Support of Greater Everglades
Ecosystem Restoration).
We will use established sampling methodologies such as PVC refugia
trapping to investigate amphibian occupancy rates, develop new methods for
sampling across hydroperiod gradients (drift fence arrays, PVC arrays), and use
newly developed statistical techniques to estimate the proportion of area
occupied by and to define amphibian communities. Our objectives include:
- Define amphibian communities appropriate for
evaluating restoration success.
- Develop methods for measuring the area occupancy
of amphibian communities across habitats and environmental gradients.
- Investigate the relationship of occupancy with
hydroperiod and other environmental factors.
- Develop restoration targets for the amphibian
community of the Everglades.
- Develop a restoration tool for amphibian
communities that measures restoration success and compares restoration
alternatives.
- Develop an index of biological integrity for
amphibians that provides a framework for scientifically defensible
decisions by restoration managers.
Work to be undertaken
during the proposal year and a description of the methods and procedures:
During FY05, we will concentrate our work on:
- Developing methods for
defining amphibian communities.
- Developing methods for
measuring the occupancy rate of communities across habitats and hydroperiod
gradients.
- Establishing restoration
targets for amphibian communities in appropriate habitats.
- Developing models and
methods to measure restoration success across these communities and compare
restoration alternatives.
- Developing an overall
index of amphibian community integrity.
Duellman and
Schwartz (1958) produced the first scientific survey of the amphibians of south
Florida. This work serves as an
excellent reference for the historical distribution of many species before the
extensive habitat loss in south Florida during the second half of the 20th century. Meshaka et al. (2000)
produced a species list of the herpetofauna for ENP, but little information
about the habitat associations and population status of the species was
contained in that report.
Dalrymple (1988) provided a good description of the herpetofauna of the
Long Pine Key area in ENP, but no attempt has been made to sample amphibians
throughout the Everglades.
We will use 2 primary methods to accomplish the objectives of the
project:
- Proportion
area occupied (PAO) by a species.
- Vocalization
survey
- Time-constrained
searches
- Proportion area occupied by a community.
Proportion area occupied by a species.-- One problem with many of the methods
used to sample amphibians
is the lack of any control of the myriad environmental factors that affect the
behavior and activity of the animals.
Abiotic factors like temperature, humidity and hydrology as well as
biotic factors like the presence of predators or conspecifics can affect the
observability of amphibians. The
observability of species' population is a function of the population size, the
behavior of the individuals, and the ability of the observer to locate the
animals in the particular habitat.
Many monitoring programs simply count animals and do not control for
this observability or capture probability (p).
Therefore, comparisons over time or space are not possible or are
biased. If the monitoring program
can assume the cost of marking individual animals, then p can be determined and population size or
density determined (standard mark-recapture methods, see Williams, et al. 2002). However, this would be cost prohibitive
in a monitoring program for all amphibian species throughout the
Everglades. MacKenzie, et al.
(2002) has developed a novel approach to this problem. Rather than mark the individual, we
"mark" the species. Therefore,
presence/absence data from several plots within a habitat (or along a
hydroperiod gradient in our study) provides an estimate of p and allows estimation of the proportion
of a stratum occupied by a given species at a given time.
Sampling
units will be chosen randomly within each stratum. Within Everglades National Park these are along the Main
Park Road and Context Road. We
will choose 15 sites along each road accessed by foot. The sites will be
located within 300 to 900 feet of the road. In Water Conservation Area 3A, we will select 15 sites in
each stratum along a North-South transect from I75 to SR41. Each stratum will be defined by the
hydroperiod observed from existing hydrologic data and habitat type as defined
by existing GIS vegetation layers.
For hydropattern, a stratum will be defined for each 50 day difference
(0-50, 51-100, 101-150, 151-201, 251-300, 301-365 days). Sites will be visited twice biweekly,
April through September.
Our standardized sampling unit will be a circular plot of 20m
radius. Plots will be sampled
after dark to increase the probability of observing nocturnal amphibians. At each plot 2-3 person crews will begin by listening for anuran
vocalizations for 10 minutes. The
abundance of each species will be categorized as: no frogs calling, one frog
calling, 2-5 calling, 6-10 calling, >10 calling, or large chorus. The intensity of the vocalizations will
be categorized as: no frogs calling, occasional, frequent, or continuous. After the vocalization survey, we will
perform a 30-minute visual encounter survey (VES) in each plot. During this time, all individual
amphibians observed will be identified to species and captured if possible. We will record the species, categorize
the age (egg, larvae, juvenile, sub-adult, or adult), measure and record the
snout-to-vent length and record the sex if it can be determined. The animal will then be released at the
original capture site. We also
will record the substrate and perch height of the animal. A University of Florida Institutional
Animal Care and Use Committee approval will be obtained for animal
capture. In addition to VES, in
plots that are completely flooded, we will use dipnets and funnel traps to
attempt to capture aquatic amphibians.
We also will record several ancillary variables at each plot (air
temperature, relative humidity, presence of water, water temperature, wind
speed, cloud cover). If any
animals are captured show signs of disease or are new exotic species, we will
collect them for health assessment by the USGS National Wildlife Health Center
and/or identification and preservation by the Park.
In addition, a maximum of 20-1m tall, 5 cm diameter PVC removable
pipes will be installed in each site for refugia of treefrog species. During
each visit, animals will be removed from the pipe for identification and
measurement as outlined above. All
animals will be released into the original PVC refugia. All PVC will be removed at the end of
the study.
At 10 sites in ENP (5 along Context Road and 5 along Main Park Road) we will
install a 20m drift fence for capture of aquatic salamanders. The drift fence will consist of 20m of
removable erosion control fence with a funnel trap incorporated at each end and
in the center. Traps will be
placed along the fence for 5 consecutive days once per month during May through
October. The traps will be checked
each day in the morning to minimize heat stress on captured animals. Animals will be measured as outlined
above and released at the capture site.
All traps and drift fences will be removed during non-capture
periods. All drift fences and
traps will be removed at the end of the study. Both drift fences and PVC refugia will be placed behind
vegetation to minimize views from the road if possible.
Individual species capture histories
(matrix of presence/absence of each species at a sampling period and plot) and
corresponding covariates (habitat, hydroperiod, temperature, humidity) will be
assembled. We will then estimate
the proportion of each stratum occupied by a species and the capture
probability (using MLE and the logistic regression for covariates; MacKenzie et
al. 2002). The best model will
minimize AIC and adequately estimate the parameters in the model (the candidate
model list will be developed a priori based on ecological knowledge and will not include all possible
combinations). We can then use
these estimates to construct appropriate communities for each stratum (see
proportion of area occupied by a community below).
Proportion area occupied
by a community.-- Given that species occupancy rates differ across
hydroperiod gradients and that hydrology is the controlling factor of this
difference (see above), we can begin to construct "communities." In Figure 1 below (letters represent
species, the size of the circle represents PAO, numbers represent hydroperiod),
we can see that in short hydroperiod sites, species A and D dominate. However, as we move to longer
hydroperiod sites, other species emerge as the dominate species in the
community. This pattern of species
composition and PAO forms the set of "communities" along the hydroperiod
gradient.
 |
| Figure 1. Conceptual view of proportion of area occupied by communities of amphibians across a gradient of hydroperiod in the Everglades. [larger image] |
We have seen this pattern begins to emerge in preliminary data from the Everglades (Table 1).
| Table 1. Proportion Area Occupied values for amphibian species in the Everglades across a gradient of hydroperiod (values are an estimate of the proportion of a stratum occupied by that species): |
|
Hydroperiod
|
Cricket Frog
|
Southern Toad
|
Squirrel Treefrog
|
Pigfrog
|
Leopard Frog
|
|
Short
|
0.0000
|
0.5277
|
0.7058
|
0.0000
|
0.3101
|
|
|
0.0000
|
0.5155
|
0.6495
|
0.3123
|
1.0000
|
|
|
0.1525
|
1.0000
|
0.1865
|
1.0000
|
0.8564
|
|
|
0.3391
|
0.0000
|
1.0000
|
0.8708
|
0.8646
|
|
Long
|
0.7080
|
0.4333
|
0.1718
|
0.7068
|
0.3558
|
At present, the method for defining and then
predicting community composition and PAO is not complete. This study will develop this
methodology for the Everglades.
Index of Biological Integrity.-- Indices of biological integrity (IBI) were originally developed to assess conditions of
riverine systems (Karr 1991, 1993) and also have been developed successfully
for use in terrestrial environments (O'Connell et al. 1998). The basic premise of IBI's is that a
range of conditions of ecological integrity can be defined based on the
structure and composition of a selected biological community (e.g. amphibians,
fish, birds, macroinvertebrates).
The concept of biological integrity provides an ecologically-based
framework in which species-assemblage data can be ranked in a manner that is
more informative than traditional measures such as richness and diversity (Karr
and Dudley 1981, Brooks et al. 1998).
Therefore, the final step in this project will be to develop an
amphibian community index (ACI) for evaluating the success of restoration and
management of Greater Everglades Ecosystems. The ACI will be modeled after previously developed IBI's (Cronquist and Brooks 1991, Karr 1991,1993, Books et al. 1998, O'Connell et al.
1998). Essentially, we will use
the PAO of communities estimated above to index or define the integrity of a
given stratum. As restoration
proceeds, we can use changes in the index to make informed management decisions
and to measure success. Further,
we can use the pattern of these communities based on hydopattern to develop
restoration targets and to compare alternatives. By providing a reliable and repeatable measure of ecological
quality an ACI will help managers reach scientifically defensible decisions
(Brooks et al. 1998).
Literature Cited:
Boughton, R. G., J.
Staiger, and R. Franz. 2000. Use of PVC pipe refugia as a sampling
technique for hylid treefrogs. American
Midland Naturalist 144: 168-177.
Brooks, R.P., O'Connell,
T.J., Wardrop, D.H., and Jackson, L.E.: 1998, 'Towards a Regional Index of Biological Integrity:
The Example for Forested Riparian Systems,'Environmental Monitoring and Assessment, 51, 131-143.
Croonquist, M.J. and Brooks, R.P.: 1991, 'Use of avian and mammalian guilds as indicators of cumulative
impacts in riparian-wetland areas,' Environmental Management 15,
701-714.
Dalrymple, G. H.
1988. The herpetofauna of Long Pine Key, Everglades National Park, in
relation to vegetation and hydrology.
Pp 72-86 In: Szaro, R. C.,
K. E. Stevenson, and D. R. Patton, eds.
The management of amphibians, reptiles and small mammals in North
America. U.S. Dept. of
Agriculture, U.S. Forest Service Symposium, Gen. Tech. Rept. RM-166, Flagstaff,
AZ.
Donnelly, M. A., C.
Guyer, J. E. Juterbock, and R. A. Alford.
1994. Techniques for
marking amphibians. In Heyer, W. R., M. A. Donnelly, R. W. McDiarmid, L. C.
Hayek, and M. S. Foster, editors.
Measuring and monitoring biological diversity: Standard methods for
amphibians. Smithsonian
Institution. Washington, D.C.
Duellman, W.E. and A.
Schwartz. 1958. Amphibians and
reptiles of southern Florida.
Bull. Florida State Mus., no. 3.
Enge, K. M. 1997. A standardized protocol for drift-fence surveys. Florida Game and Fresh Water Fish
Commission Technical Report No. 14.
Tallahassee. 69 pp.
Karr, J.R. : 1991,
'Biological integrity: a long-neglected aspect of water resource management, 'Ecological
Applications 1, 66-84.
Karr, J.R. : 1993, 'Defining
and assessing ecological integrity: beyond water quality,' Environmental
Toxicology and Chemistry 12, 1521-1531.
Karr, J.R. and Dudley, D.R. :
1981, 'Ecological perspective on water quality goals,' Environmental Management 5, 55-68.
MacKenzie, D.I., J.D.
Nichols, G.B. Lachman, S. Droege, J.A. Royle, and C.A. Langtimm. 2002.
Estimating site occupancy rates when detection probabilities are less than one,
Ecology. In Press.
Meshaka, W.E., W.F.
Loftus, and T. Steiner. 2000. The Herpetofauna of Everglades National
Park. Florida Scientist 63(2):
84-103.
O'Connell, T. J., Jackson,
L.E., and Brooks, R.P. : 1998, 'A Bird Community Index of Biotic Integrity
for the Mid-Atlantic Highlands,' Environmental Monitoring and Assessment, 51,
145-156.
Williams, B.K., J.D. Nichols, and M.J. Conroy. 2002.
Analysis and management of animal populations. Academic Press, London. 817 pp.
Specific Task
Product(s):
- Tools and scientific data necessary for
evaluation of restoration success and comparison of restoration alternatives.
- Methods and data necessary for RECOVER's adaptive
assessment process and monitoring program.
- Development of a cost-effective monitoring
program for amphibians.
- Development of performance measures for amphibian
communities.
- Peer-reviewed publications and published
methodology for evaluation of restoration success.
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