Prime real estate matters: effects of population density on spatial distributions of a Neotropical glassfrog Nicole F. Angeli 1,2 , Grace V. DiRenzo 2 , Alexander Cunha 3 , and Karen R. Lips 2 1 Applied Biodiversity Sciences, Texas A&M University 2 Department of Biology, University of Maryland, College Park 3 Organismal and Evolutionary Ecology Program, Harvard University
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Effects of density on spacing patterns and habitat associations of a Neotropical Glassfrog
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Prime real estate matters: effects of population density on spatial distributions of a
Neotropical glassfrog
Nicole F. Angeli1,2, Grace V. DiRenzo2,Alexander Cunha3, and Karen R. Lips2
1Applied Biodiversity Sciences, Texas A&M University2Department of Biology, University of Maryland, College Park
3Organismal and Evolutionary Ecology Program, Harvard University
Random
Different patterns predict processes
Many Neotropical stream frogs are aggregated (Atelopus varius, Pounds and Crump, 1987; Craugastor punctariolus, Ryan, Lips and Eichholz, 2008)
Uniform Clustered
(Clark, 1946; Diggle, 1985; Ripley, 1991; Bivand et al., 2008)
Clustered animals may fight for resources
‘Limiting wars’ Maynard Smith and Price, 1973
Espadarana prosoblepon; Jacobson, 1985
Espadarana prosoblepon are aggregated (CD=3.215, Witters and Lips, unpub)
Why do E. prosoblepon cluster, and why do we care?
Declines in amphibian community at Omar Torrijos H.D. NP, El Copé, Coclé, Panama
t =-24.44, df=486, P < 0.0001 Lips et al. 2006 PNAS
Quantify lethal and non-lethal effects of declines
Males: night, on stream banks;
Fighting, calling, mating;
lifespan ~ 5 years
(Jacobson, 1985; Guayasamin et al., 2009)
Females: cryptic
(Savage, 2002)
Juveniles: hatch and fall into
stream leaf litter to develop (Cisneros-Heredia et al., 2006)
Espadarana (Centrolene) prosoblepon
Espadarana prosoblepon
Can the spatial organization of E. prosoblepon change over time and space?
1. Does clustering occur on the streams?
Map male E. prosoblepon along streams
2. Will clustering change before and after Bd?
Detect changes in dispersion at varying densities
3. Are clusters based on resources or interactions?
Quantify animal arrangement and habitat
4-200 m permanent stream transects
LoopCascadaSilenciosaGuabal
Visual Encounter Surveys extending 2 m onto stream banks
Adults sexed by calling and presence of humeral spines
Individual Toe Clips
(Heyer et al., 1994)
Microhabitat variables
Canopy
Veg at 0.5 m
Veg at 1.0 m
Veg at 1.5 m
Sand
Gravel
Cobble
Boulder
CWD
Stream Width
Stream Depth
Complete Data Set:
X=13 years
225 surveys
480 meters of habitat data
N= 1,678 male E. prosoblepon881 unique males
- X-Y locality data- Individual marks
Density of captures during 225 surveys annualized over 13 years
Loop Guabal Cascada SilenciosaPercent change in
abundance after Bd -46.3% -5.9% -68.3% -31.8%
Years with frogs: 11 11 8 7
Low intensity, no frogs
a. Visualize clusters using density maps smoothed with Gaussian kernel (Baddeley and Turner, 2005)
b. Kuldorff (2006) SatScanStatistic to identify clusters independent of space, time
Distance from stream (meters)
1. Identify and compare hotspots over time
Tran
sect
Le
ngt
h (
me
ters
)
2. Detect changes in dispersion at varying densities
a. Detect patterns using linearized Ripley’s Kb. Use derived inflection points to calculate nearest