Transcript Managing habitat for Eastern tiger & other Ambystomid salamanders

Managing habitat for the
eastern tiger salamander
and other Ambystomid
salamander species
Valorie R. Titus, PhD
American Public University System
Amphibian Decline
Climate Change
Invasive Species
Pollution
Pet Trade
Disease
Habitat Loss
Adult A. tigrinum
Management Issues
Habitat Use/Quality
Movement/Buffer Zones
Population genetics
Relocation, Repatriation,
Translocation
Typical A. tigrinum breeding pond
Eastern Tiger Salamander
Ambystoma tigrinum
NYS Endangered
Decreasing throughout
their range
Many areas on Long
Island are in danger of
development
Pre-metamorphic A. tigrinum
Current Range
http://www.dec.state.ny.us/website/dfwmr/wildlife/endspec/tisafs.html
Historic Range in N.Y.
Current Range in N.Y.
http://www.dec.state.ny.us/website/dfwmr/wildlife/herp/eatisala.gif
Current Legal
Protection
New York State Freshwater
Wetland Act: 30 m buffer
surrounding wetlands
NYS DEC
Recommendations: 164 m,
no more than 50% upland
habitat within 305 m of
breeding pond be converted
to unusable habitat (based
on Semlitsch 1998)
Recent metamorph
Movements
Brookhaven National
Laboratory, Long Island, N.Y.
Over 5000 acres
22+ confirmed salamander
ponds on site
3 Focal Ponds: L1, L3, L7
Tiger Salamander management
and monitoring protocols already
in place
Methods
Collected males and
females upon
emigration from
breeding ponds
Collected juveniles
upon emigration or just
before final
metamorphosis
Pre-metamorphic A. tigrinum
Results
Movements at night
during rain event
Some short movements
after implant
replacement
Avoided open fields,
development, planted
white pine stands
Adult A. tigrinum outside burrow
Results
Tracked 33 males, 26
females, 47
metamorphs
Predation: Bullfrog,
Eastern Hognose
Snake, Raccoon,
Northern Short-Tailed
Shrew, Eastern Ribbon
Snake
Radiotransmitter with
B. brevicauda tooth marks
Results
Recovered a greater proportion of
implants from males (72.2%, 24 of
33) than females (30%, 8 of 26)
(Fisher Exact Probability, P=0.001)
No difference between number of
implants recovered (N=25) and lost
(N=22) for juveniles
More likely to recover implant from
juveniles remaining closer to the
breeding pond (Z=2.750, P=0.006)
Juvenile A. tigrinum size
differences
Conclusions
Predation may be higher closer to breeding pond
Males may stay closer as a reproductive strategy
Females may move farther to reduce resource
competition
Optimal pond conditions during development may
influence juvenile dispersal
Traditionally calculated buffer zones may be
inadequate for this species
Fails to protect 20% of individuals in this study,
however, incorporating a 50 m edge effect, only
protects 62%
May encompass unsuitable habitat and reduce
availability of good habitat
Pre-metamorphic A. tigrinum
Connectivity
Fragmented landscapes
resulting from anthropogenic
habitat modification can have a
significant impact on dispersal,
gene flow, and persistence of
wildlife populations
Reduced genetic variation can
severely compromise the ability
of a population to respond to
subsequent environmental
change
Adult A. tigrinum
Goals
Assess population
genetic diversity of
remaining tiger
salamander populations
Quantify genetic and
landscape connectivity
among ponds and
populations to identify
potential corridors and
barriers to migration
Adult A. tigrinum
Methods
Collected samples from 17
breeding sites across Long
Island and 9 sites in New Jersey
Collected as many samples as
possible (N=2-93) from each site
Genotyped 439 individuals
across 12 microsatellite loci
Samples included toe and tail
clips and individual eggs from
egg masses
A. tigrinum egg mass
Results- Regional Population
Structure and Migration
Low allelic diversity
Markers not highly
polymorphic (1-13 alleles)
Mean numbers of alleles
ranged from 1.1 to 3.3 in
New York and 1.7 to 2.4 in
New Jersey
GENEALEX version 6
(Peakall and Smouse 2006)
GENEALEX version 6 (Peakall and Smouse 2006)
Results- Regional Population
Structure and Migration
Results- Regional Population
Structure and Migration
High levels of population
differentiation between NY and NJ
(average Fst=0.217) (FSTAT
Goudet 1995; Weir and
Cockerham 1984).
Few individuals were assigned to
the pond at which they were
sampled with either 80% or 95%
confidence, and many of these
individuals were assigned to other
ponds with high confidence
(GENECLASS2; Piry et al. 2004)
Results- Landscape
Barriers to Migration
Defined land cover resistance
values from Compton et al. (2007)
and Greenwald et al. (2009)
Calculated euclidean distance,
euclidean resistance, and surface
resistance (using CIRCUITSCAPE
version 3.3; McRae and Shah
2009);
Correlated these values with Fst
using a Mantel test (Rosenburg and
Anderson 2011)
Adult A. tigrinum in burrow
Results- Landscape
Barriers to Migration
No relationship between
connectivity indices and Fst in
either New York (euclidean
distance: r = -0.044, p = 0.827;
euclidean resistance: r = -0.047,
p = 0.812; surface resistance: r =
-0.056, p = 0.786) or New Jersey
(euclidean distance: r = 0.120, p
= 0.388; euclidean resistance: r =
0.183, p = 0.312; surface
resistance: r = 0.226, p = 0.246)
No relationship between
Euclidean distance and
assignment probabilities in NY
(R2 = 0.0005, P = 0.791), but
significant for NJ (R2 = 0.361, P =
0.00001)
Conclusions
Low allelic diversity; likely from
few migrants during
Pleistocene (Church et al.
2002)
May make whole population
susceptible to collapse in case
of catastrophic event
High risk of inbreeding
depression if ponds become
more isolated from each other
Conclusions
3 distinct genetic demes; while
evidence of admixture, this is
likely due to ancestral
polymorphism rather than
gene flow between NY and NJ
The second NY deme is
centrally located and within 10
m of each other; likely caused
by wetland remediation from
2005-2007
Conclusions
Assignment probabilities provide
evidence of recent migration
between several ponds
Difference between NY and NJ is
likely due to distance between
ponds
Corridors appear to be present in
both NY and NJ, but no
relationship between
distance/land cover and Fst
Management
Calculate protection (buffer
zones) on a case-by-case
basis
Estimate probable dispersal
habitat and determine
available corridors
Individual breeding ponds can
be susceptible to
perturbations that may limit
migration and dispersal
So What?
Global amphibian declines
Desire to know how to properly
conserve and manage this and
other amphibian species
Disease outbreaks; already
confirmed Bd and Ranavirus on
site
Can we actively manage this
species (e.g. relocation,
assisted migration)?
Literature Cited
Church, SA, Kraus JM, Mitchell JC, Church DR, Taylor DR (2002) Evidence for multiple Pleistocene refugia in the postglacial expansion of the eastern
tiger salamander, Ambystoma tigrinum tigrinum. Evolution 52:372-383
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mitochondrial DNA restriction data Genetics 131:479-491.
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McRae BH, Shah VB (2009) Circuitscape user’s guide. The University of California, Santa Barbara. Available at: http://www.circuitscape.org.
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Acknowledgements
NYS DEC Project MOU # AM
05513
Brookhaven National Laboratory
NYS DEC
Foundation for Ecological Research
in the Northeast (FERN)
Dave Golden and the Endangered
and Nongame Species Program of
the New Jersey Division of Fish
and Wildlife
Upstate Herpetolgical Society
Acknowledgements
Dr. Dale Madison
Dr. Tim Green
Dr. Kelly Zamudio
Al Breisch
Dr. Dan Rosenblatt
Dr. Julian Shepherd
Dr. Richard Andrus
Dr. Matthew Parker
Acknowledgements
Thank you to interns and fellow
students: Sarah, Chauncey,
Wendy, Frank, Jeremy, Jennifer,
Esperanza, Stephen, Sarah,
Emily, Carmen, Renee,
Stephanie, Doris, Rachel, Dane,
Katie, Kristine, Susan, Diana,
Tyra, Shirin, Lauren, Matt,
Miranda, Becky, Mike, Omar,
Andy, Nate, Ellie, Jennifer,
Miranda, Heather, Bri, Jin Joo,
Sarah, Clara, Dave, Rayna,
Angie, and Gui