Opposing mechanisms drive diversity patterns of core and ...€¦ · Opposing mechanisms drive diversity patterns of core and occasional bird species ESA Meeting 8.12.2011 Environmental

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

S5

S6

S4

S3

S8 S1

S7

S9


Lincoln’s Sparrow Cliff Swallow


SPECIES TEMPORAL FREQUENCY



COMMUNITIES ARE BIMODAL



COMMUNITIES ARE BIMODAL



CORE AND OCCASIONAL SPECIES DEFINITION


Core Species

Maintain population at site

Occur via population

dynamics

Occasional Species

Do not maintain population

Occur via dispersal


BIOLOGICAL DEFINITION



SPECIES RICHNESS

S2

S5

S6

S4

S3

S8 S1

S7

S9


Core Species

Local factors

– Habitat quality

– Local climate

Occasional Species

Regional factors

– Landscape heterogeneity

– Size of regional species pool


FACTORS AFFECTING SPECIES RICHNESS


Core Species Occasional Species

Analysis

HYPOTHESES


Core Species Occasional Species

Analysis

HYPOTHESES


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


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


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


Linear Models: Core and occasional richness ~

Single variable models

Combinations of variables

– Variance partitioning with pairs of models

Analysis

ANALYSIS


Results

SPECIES RICHNESS MAPS


Results

SPECIES RICHNESS MAPS


Core Occasional

Results

NDVI


Core Occasional

Results

ELEVATIONAL VARIANCE


Results

ENVIRONMENTAL CORRELATES OF RICHNESS


Results

MULTIVARIATE ANALYSES


North American geography causes mechanisms

that drive core and occasional diversity to oppose

each other.

Discussion

TWO CONCLUSIONS


Discussion

PROPORTION OF OCCASIONAL SPECIES


Colorado North Carolina

Core Species 25 59

Occasional Species 31 7

Total Species 75 75

Discussion

SITE COMPARISON


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


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/

http://pwrc.usgs.gov/

http://lpdaac.usgs.gov/


Supplemental Material

EFFECT OF TIME WINDOW



CORE-OCCASIONAL DEFINITION THRESHOLD

Core: >75%

Occasional: <25%

Core: >50%

Occasional: <50%



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


Results

ENVIRONMENTAL CORRELATES OF RICHNESS


Introduction

PATTERNS OF SPECIES RICHNESS

S2

S5

S6

S4

S3

S8 S1

S7

S9


Introduction

RELAXING AN ASSUMPTION

S5

S6

S4

S3

S8 S1

S7

S9

S2


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

Documents

Opposing mechanisms drive diversity patterns of core and ...€¦ · Opposing mechanisms drive diversity patterns of core and occasional bird species ESA Meeting 8.12.2011 Environmental