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Opposing mechanisms drive
diversity patterns of core and
occasional bird species
Jessica R. Coyle1 Allen H. Hurlbert1 Ethan P. White2
1 University of North Carolina, Chapel Hill, NC 2 Utah State University, Logan, UT
ESA Meeting, August 12th, 2011
Opposing mechanisms drive diversity patterns of core and occasional bird species ESA Meeting 8.12.2011
Defining Core and Occasional Species
SPECIES RICHNESS
S2
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S7
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Opposing mechanisms drive diversity patterns of core and occasional bird species ESA Meeting 8.12.2011
Lincoln’s Sparrow Cliff Swallow
Defining Core and Occasional Species
SPECIES TEMPORAL FREQUENCY
Opposing mechanisms drive diversity patterns of core and occasional bird species ESA Meeting 8.12.2011
Defining Core and Occasional Species
COMMUNITIES ARE BIMODAL
Opposing mechanisms drive diversity patterns of core and occasional bird species ESA Meeting 8.12.2011
Defining Core and Occasional Species
COMMUNITIES ARE BIMODAL
Opposing mechanisms drive diversity patterns of core and occasional bird species ESA Meeting 8.12.2011
Defining Core and Occasional Species
CORE AND OCCASIONAL SPECIES DEFINITION
Opposing mechanisms drive diversity patterns of core and occasional bird species ESA Meeting 8.12.2011
Core Species
Maintain population at site
Occur via population
dynamics
Occasional Species
Do not maintain population
Occur via dispersal
Defining Core and Occasional Species
BIOLOGICAL DEFINITION
Opposing mechanisms drive diversity patterns of core and occasional bird species ESA Meeting 8.12.2011
Defining Core and Occasional Species
SPECIES RICHNESS
S2
S5
S6
S4
S3
S8 S1
S7
S9
Opposing mechanisms drive diversity patterns of core and occasional bird species ESA Meeting 8.12.2011
Core Species
Local factors
– Habitat quality
– Local climate
Occasional Species
Regional factors
– Landscape heterogeneity
– Size of regional species pool
Defining Core and Occasional Species
FACTORS AFFECTING SPECIES RICHNESS
Opposing mechanisms drive diversity patterns of core and occasional bird species ESA Meeting 8.12.2011
Core Species Occasional Species
Analysis
HYPOTHESES
Opposing mechanisms drive diversity patterns of core and occasional bird species ESA Meeting 8.12.2011
Core Species Occasional Species
Analysis
HYPOTHESES
Opposing mechanisms drive diversity patterns of core and occasional bird species ESA Meeting 8.12.2011
Avian Species Richness
Calculated for 492 BBS routes surveyed 1996-2010
Core-Occasional designation of species on route
based on all years surveyed
Analysis
DATA
Opposing mechanisms drive diversity patterns of core and occasional bird species ESA Meeting 8.12.2011
Environmental Data
Climate and elevation data from WorldClim
Summer vegetation indices from MODIS
Calculated mean and variance of environmental
variables within neighborhood of each route.
Analysis
DATA
Opposing mechanisms drive diversity patterns of core and occasional bird species ESA Meeting 8.12.2011
Environmental Data
Climate and elevation data from WorldClim
Summer vegetation indices from MODIS
Calculated mean and variance of environmental
variables within neighborhood of each route.
(Local environment) (Spatial heterogeneity)
Analysis
DATA
Opposing mechanisms drive diversity patterns of core and occasional bird species ESA Meeting 8.12.2011
Linear Models: Core and occasional richness ~
Single variable models
Combinations of variables
– Variance partitioning with pairs of models
Analysis
ANALYSIS
Opposing mechanisms drive diversity patterns of core and occasional bird species ESA Meeting 8.12.2011
Results
SPECIES RICHNESS MAPS
Opposing mechanisms drive diversity patterns of core and occasional bird species ESA Meeting 8.12.2011
Results
SPECIES RICHNESS MAPS
Opposing mechanisms drive diversity patterns of core and occasional bird species ESA Meeting 8.12.2011
Core Occasional
Results
NDVI
Opposing mechanisms drive diversity patterns of core and occasional bird species ESA Meeting 8.12.2011
Core Occasional
Results
ELEVATIONAL VARIANCE
Opposing mechanisms drive diversity patterns of core and occasional bird species ESA Meeting 8.12.2011
Results
ENVIRONMENTAL CORRELATES OF RICHNESS
Opposing mechanisms drive diversity patterns of core and occasional bird species ESA Meeting 8.12.2011
Results
MULTIVARIATE ANALYSES
Opposing mechanisms drive diversity patterns of core and occasional bird species ESA Meeting 8.12.2011
North American geography causes mechanisms
that drive core and occasional diversity to oppose
each other.
Discussion
TWO CONCLUSIONS
Opposing mechanisms drive diversity patterns of core and occasional bird species ESA Meeting 8.12.2011
Discussion
PROPORTION OF OCCASIONAL SPECIES
Opposing mechanisms drive diversity patterns of core and occasional bird species ESA Meeting 8.12.2011
Colorado North Carolina
Core Species 25 59
Occasional Species 31 7
Total Species 75 75
Discussion
SITE COMPARISON
Opposing mechanisms drive diversity patterns of core and occasional bird species ESA Meeting 8.12.2011
North American geography causes mechanisms
that drive core and occasional diversity to oppose
each other.
It is important to distinguish between core and
occasional species when interpreting species
richness, since these two groups have different
roles in the community.
Discussion
TWO CONCLUSIONS
Opposing mechanisms drive diversity patterns of core and occasional bird species ESA Meeting 8.12.2011
Acknowledgements
ACKNOWLEDGEMENTS
The Hurlbert Lab
Dan McGlinn
James Stegan
Katie Becraft
Brian Evans
Funding
Royster Society of Fellows
and the Biology Department
University of North Carolina,
Chapel Hill
Data
The North American
Breeding Bird Survey
USGS Patuxent Wildlife
Research Center
http://pwrc.usgs.gov/
MODIS Products
LP DAAC
http://lpdaac.usgs.gov/
Opposing mechanisms drive diversity patterns of core and occasional bird species ESA Meeting 8.12.2011
Supplemental Material
EFFECT OF TIME WINDOW
Opposing mechanisms drive diversity patterns of core and occasional bird species ESA Meeting 8.12.2011
Supplemental Material
CORE-OCCASIONAL DEFINITION THRESHOLD
Core: >75%
Occasional: <25%
Core: >50%
Occasional: <50%
Opposing mechanisms drive diversity patterns of core and occasional bird species ESA Meeting 8.12.2011
Supplemental Material
PCA LOADINGS Comp 1 Comp 2
Summer NDVI -0.249 -0.370
Annual precipitation -0.312 -0.427
Minimum precipitation -0.272 -0.317
Maximum precipitation -0.233 -0.376
Mean annual temperature -0.269 0.074
Maximum temperature -0.205 0.288
Summer NDVI (var) 0.081 -0.050
Mean annual temperature
(var) 0.360 -0.248
Elevation (var) 0.375 -0.224
Elevation 0.383 0.060
Annual precipitation (var) 0.190 -0.423
Maximum temperature (var) 0.371 -0.231
Standard deviation 2.252 1.569
Proportion of variance 0.424 0.205
Cumulative proportion 0.424 0.629
Opposing mechanisms drive diversity patterns of core and occasional bird species ESA Meeting 8.12.2011
Results
ENVIRONMENTAL CORRELATES OF RICHNESS
Opposing mechanisms drive diversity patterns of core and occasional bird species ESA Meeting 8.13.2011
Introduction
PATTERNS OF SPECIES RICHNESS
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Opposing mechanisms drive diversity patterns of core and occasional bird species ESA Meeting 8.13.2011
Introduction
RELAXING AN ASSUMPTION
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Opposing mechanisms drive diversity patterns of core and occasional bird species ESA Meeting 8.12.2011
Avian communities are comprised of core and
occasional species.
Core species richness is correlated with the local
environment.
Occasional species richness is correlated with
regional factors.
Discussion
SUMMARY