Scale-dependent invasion patterns and community assembly in the Southeastern US flora

Scale-dependent invasion patterns Scale-dependent invasion patterns and community assembly and community assembly in the Southeastern in the Southeastern US floraUS flora

Jason FridleyJason FridleyUNC – Chapel HillUNC – Chapel Hill

AcknowledgementsAcknowledgementsCollaborators:Collaborators:Becky Brown, Eastern Washington UniversityBecky Brown, Eastern Washington UniversityMike Palmer, Oklahoma State UniversityMike Palmer, Oklahoma State UniversityJohn Bruno, UNCJohn Bruno, UNCPeter White, UNCPeter White, UNCBob Peet, UNCBob Peet, UNCAlan Weakley, UNCAlan Weakley, UNC Data:Data:Carolina Vegetation SurveyCarolina Vegetation SurveyNorth Carolina Botanical GardenNorth Carolina Botanical Garden

Funding:Funding:National Parks Ecological Research FellowshipNational Parks Ecological Research Fellowship

Andrew W. Mellon Foundation (NPS, NPF, ESA)Andrew W. Mellon Foundation (NPS, NPF, ESA)

Exotic speciesExotic speciesContributions of communityContributions of community

and landscape ecologyand landscape ecology

•Do biotic/community properties Do biotic/community properties contribute to invasion resistance?contribute to invasion resistance?

•Are exotic species ecologically unique?Are exotic species ecologically unique?

•Do exotic species alter assembly Do exotic species alter assembly processes in native communities?processes in native communities?

•Do exotic/invasive species favor Do exotic/invasive species favor particular environments?particular environments?

•Are communities saturated with species?Are communities saturated with species?

Temperate vs.Tropical

States, Provinces

Counties

Landscapes,Watersheds

Communities

Neighborhoods

109

103

105

107

101

10-3

10-1

SC

AL

E(h

ect

are

s)

Correlation of Native andExotic Species Richness

0negative positive

observations

experiments

?

Pattern and Process in Species InvasionsPattern and Process in Species Invasions

Temperate vs.Tropical

States, Provinces

Counties

Landscapes,Watersheds

Communities

Neighborhoods

109

103

105

107

101

10-3

10-1

SC

AL

E(h

ect

are

s)

Correlation of Native andExotic Species Richness

0negative positive

observations

experiments

?

Pattern and Process in Species InvasionsPattern and Process in Species Invasions

Community ecologyCommunity ecology

Landscape ecologyLandscape ecology

BiogeographyBiogeography

Scalin

g ru

les?

Scalin

g ru

les?

-2 0 2 4 6 8 10 12 14

Log10 Area (m2)

0

1

2

3

4

5

6

Lo

g10

Sp

ecie

s R

ich

nes

sScaling rules of species richness...Scaling rules of species richness...

the species-area curvethe species-area curve

-2 0 2 4 6 8 10 12 14

Log10 Area (m2)

0

1

2

3

4

5

6

Lo

g10

Sp

ecie

s R

ich

nes

sHow do scaling rules represent How do scaling rules represent

processprocess??

Biotic constraintsBiotic constraints

Environmental variance

Environmental variance

Dispersal constraintsDispersal constraints

-2 0 2 4 6 8 10 12 14

Log10 Area (m2)

0

1

2

3

4

5

6

Lo

g10

Sp

ecie

s R

ich

nes

sCarolina Vegetation Survey: 1988 to presentCarolina Vegetation Survey: 1988 to present

0.01 – 1000 m2

-2 0 2 4 6 8 10 12 14

Log10 Area (m2)

0

1

2

3

4

5

6

Lo

g10

Sp

ecie

s R

ich

nes

sCarolina Vegetation SurveyCarolina Vegetation Survey

0.01 – 1000 m2

50 m

20 m

I

I

I

I

-2 0 2 4 6 8 10 12 14

Log10 Area (m2)

0

1

2

3

4

5

6

Lo

g10

Sp

ecie

s R

ich

nes

sCarolina Vegetation SurveyCarolina Vegetation Survey

0.01 – 1000 m2

50 m

20 m

I

I

I

I

0.01 m2 range: 0 to 11 species

1000 m2 range: 6 to 180 species

-2 0 2 4 6 8 10 12 14

Log10 Area (m2)

0

1

2

3

4

5

6

Lo

g10

Sp

ecie

s R

ich

nes

sFine-scale Z values: ~0.37Fine-scale Z values: ~0.37

0.01 – 1000 m2

0.1 0.2 0.3 0.4 0.5 0.6 0.7Accumulation rate (Z)

0

20

40

60

80

100

Cou

nt

95% within 0.22 and 0.5495% within 0.22 and 0.54

Body size and species poolsBody size and species pools

-2 -1 0 1 2 3

Log Area (m2)

1

10

100

Ric

hn

es

s

Spruce-fir forests

Montane rich coves

-2 0 2 4 6 8 10 12 14

Log10 Area (m2)

0

1

2

3

4

5

6

Lo

g10

Sp

ecie

s R

ich

nes

s

Z values 0.1 – 0.2?

Intermediate scales: large stands, Intermediate scales: large stands, watersheds, landscapes, natural areaswatersheds, landscapes, natural areas

Poor data!

Log Area

Lo

g S

pec

ies

Ric

hn

ess

Large-scale upturnLarge-scale upturn

Betw

een

prov

ince

s

Betw

een

prov

ince

s

Within province

Within province

Within province

Within province

Dispersal-drivenDispersal-drivenEcological equivalentsEcological equivalents

Rosenzweig 1995Rosenzweig 1995

-2 0 2 4 6 8 10 12 14

Log Area

0

1

2

3

4

5

Lo

g S

pec

ies

rich

nes

s

NC Bot GardenOeland, SwedenThe NetherlandsNC Coastal PlainHigh elevation, GSMNPShmida&Wilson (Israel)

Full-scale curvesFull-scale curves

-2 0 2 4 6 8 10 12 14

Log Area

0

1

2

3

4

5

Lo

g S

pec

ies

rich

nes

s

NC Bot GardenOeland, SwedenThe NetherlandsNC Coastal PlainHigh elevation, GSMNPShmida&Wilson (Israel)

24 x 24 km

47 x 47 km

186 x 186 km

600 x 600 km

Provinces – too big?Provinces – too big?

Consequences forConsequences forspecies invasions?species invasions?

Log Area

Lo

g S

pec

ies

Ric

hn

ess

Alternative hypothesis: Alternative hypothesis: environmental textureenvironmental texture

w/ M. Palmer and P. Whitew/ M. Palmer and P. White

Soils and geomorphology

Soils and geomorphology

High High DD

Climat

e

Climat

e

Low Low DD

Schimper’s Laws?Schimper’s Laws?

-2 0 2 4 6 8 10 12 14

Log10 Area (m2)

0

1

2

3

4

5

6

Lo

g10

Sp

ecie

s R

ich

nes

sScaling rules for species invasions?Scaling rules for species invasions?

Does exotic species richness Does exotic species richness exhibit the same scale exhibit the same scale

dependencies?dependencies?

-2 0 2 4 6 8 10 12 14

Log10 Area (m2)

0

1

2

3

4

5

6

Lo

g10

Sp

ecie

s R

ich

nes

sScaling rules for species invasions?Scaling rules for species invasions?

If exotics are less dispersal limited, should the If exotics are less dispersal limited, should the upturn be at a different scale or exist at all?upturn be at a different scale or exist at all?

Do exotics observe the same Do exotics observe the same environmental template?environmental template?

Are native communities saturated, thereby Are native communities saturated, thereby further constraining exotic establishment?further constraining exotic establishment?

-2 0 2 4 6 8 10 12 14

Log10 Area (m2)

0

1

2

3

4

5

6

Lo

g10

Sp

ecie

s R

ich

nes

sNull hypothesisNull hypothesis

If the average distribution of a native If the average distribution of a native and exotic species is the same...and exotic species is the same...

...then exotics should be a ...then exotics should be a consistent proportion of a total consistent proportion of a total

species pool.species pool.

All speciesAll species

Exotics only Exotics only

-2 0 2 4 6 8 10 12 14

Log10 Area (m2)

0

1

2

3

4

5

6

Lo

g10

Sp

ecie

s R

ich

nes

s

Hotspots?Hotspots?

Coldspots? Coldspots?

All speciesAll species

Deviations from expected curvesDeviations from expected curves

Exotics (null) Exotics (null)

Example 1: NC agroecosystemExample 1: NC agroecosystem

-6 -4 -2 0 2 4 6 8

Log10 Area (ha)

-1

0

1

2

3

4

Lo

g10

Sp

ecie

s R

ich

nes

s

Fallow cornfield:

nested 1 ha survey

(4 100 m2 modules)

Exotics only

NC+SCNC+SC+VA+GA

Southeast USAEastern USA

cont. USA

Edgecombe+Nash+Wilson

EdgecombeAll species

-6 -4 -2 0 2 4 6 8

Log10 Area (ha)

0

1

2

3

4

Lo

g10

Sp

ecie

s R

ich

nes

s

nested 0.1 ha

survey: plot 033-0O-03-3

Nolichucky RiverExotics only

NC+SCNC+SC+VA+GA


cont. USA

YanceyAll speciesYancey+Mitchell+Avery

Example 2: NC montane riverExample 2: NC montane river

180 species, 54 exotics180 species, 54 exotics

Example 3: NC piedmont forestExample 3: NC piedmont forest

-6 -4 -2 0 2 4 6 8

Log10 Area (ha)

-2

0

2

4

Lo

g10

Sp

ecie

s R

ich

nes

s

Nested 1 ha survey

(mean of 4 plots)

Hunt Arboretum

NCBG Orange5 county region

NC+SCNC+SC+VA+GA


cont. USA

Exotics only

All species

Example 4: NC piedmont forestExample 4: NC piedmont forest

-6 -4 -2 0 2 4 6 8

Log10 Area (ha)

-2

0

2

4

Lo

g10

Sp

ecie

s R

ich

nes

s

Nested survey,

Oosting plot

Duke Forest (Orange)Duke Forest (total)

Orange+Durham5 county region

NC+SCNC+SC+VA+GA


cont. USA

Oosting Plot

Exotics only

All species

1 – 10 km1 – 10 km22

-6 -4 -2 0 2 4 6 8

Log10 Area (ha)

-1.5

-1.0

-0.5

0.0

0.5

(lo

g)

Ob

serv

ed -

exp

ecte

d e

xoti

c ri

chn

ess

CornfieldHunt ArboretumMason FarmNature TrailsOosting PlotRiparian

Deviance from expected exotic richnessDeviance from expected exotic richness

Exotic enrichmentExotic enrichment

Exotic impoverishmentExotic impoverishment

-4.000 -2.000 0.000 2.000 4.000 6.000 8.000 10.000

0.000

1.000

2.000

3.000

4.000

Species-area data, Floras projectSpecies-area data, Floras projectL

og1

0 S

pe

cies

Ric

hn

ess

Log

10

Sp

eci

es R

ich

nes

s

Log10 Area (ha)Log10 Area (ha)

M. Palmer et al.M. Palmer et al.

Total speciesTotal species

ExoticsExotics

What is special about 1 - 10 kmWhat is special about 1 - 10 km22??

Oosting Plot

1 km1 km

What is special about 1 - 10 kmWhat is special about 1 - 10 km22??

NCBG lands

1 km1 km

Riparian systems - the magical ingredients:Riparian systems - the magical ingredients:• environmental favorableness (sun, nutrients)environmental favorableness (sun, nutrients)

(many exotics selected for these habitats)(many exotics selected for these habitats)

• disturbance: no biotic resistancedisturbance: no biotic resistance

• dispersal assistance: flow and floodingdispersal assistance: flow and flooding

-2 0 2 4 6 8 10 12 14

Log10 Area (m2)

0

1

2

3

4

5

6

Lo

g10

Sp

ecie

s R

ich

nes

sScaling rules for species invasionsScaling rules for species invasions

Broad-scale scaling rules (watershed Broad-scale scaling rules (watershed and above) appear remarkably similar and above) appear remarkably similar

for natives and exoticsfor natives and exotics

Rich are getting richerRich are getting richer

Finer-scale patterns usually Finer-scale patterns usually diverge from those of natives, in a diverge from those of natives, in a

habitat-dependent wayhabitat-dependent way Causes?Causes?

How well are exotic species distributed How well are exotic species distributed within habitats?within habitats?

Within regions, exotics are clustered within certain habitats.Within regions, exotics are clustered within certain habitats.• high propagule pressure high propagule pressure • high disturbance rateshigh disturbance rates• favorable environmentsfavorable environments

But how are they distributed within those habitats?But how are they distributed within those habitats?

More uniform? (widespread, previously empty niche?)More uniform? (widespread, previously empty niche?)

More clustered? (only occur in rare but ideal patches?)More clustered? (only occur in rare but ideal patches?)


Distributions of exotic Distributions of exotic species with nested species with nested plot data:plot data:

What proportion of What proportion of scale-specific scale-specific occurrencesoccurrences are are exotic?exotic?

AA

AAAA AA

AA

AA

AA

AA

AA

AA

AA

AA

B

A

C

AC

BD

A

AA

A

A

AAAA

AA

AA

AA

B

AA

C

B

A

A

D

A

A

A

C

4 natives and 1 exotic

20% exotics20% exotics



Distributions of exotic Distributions of exotic species with nested species with nested plot data:plot data:

What proportion of What proportion of scale-specific scale-specific occurrencesoccurrences are are exotic?exotic?

AA

AAAA AA

AA

AA

AA

AA

AA

AA

AA

AA

B

A

C

AC

BD

A

AA

A

A

AAAA

AA

AA

AA

B

AA

C

B

A

A

D

A

A

A

C

4 natives and 1 exotic


12.5% exotics12.5% exotics



Mountain riversMountain riversS. AppalachiansS. Appalachians

50 m

20 m

I

I

I

I

Exotic occurrences,Exotic occurrences,Riparian plotsRiparian plots

0.01 0.1 1 10 100 1000

01

02

03

04

05

06

0

% e

xo

tic

of

tota

l sp

eci

es

oc

curr

enc

es

% exotic species at each scale

Area (m2)

Cornfield bordersCornfield bordersNorth CarolinaNorth Carolina

50 m

20 m

I I

I I

0.01 0.1 1 10 100 1000

01

02

03

04

05

06

0

Exotic occurrences,Exotic occurrences,Cornfield bordersCornfield borders

% e

xo

tic

of

tota

l sp

eci

es

oc

curr

enc

es

Area (m2)


Montane upland Montane upland forests, S. Appsforests, S. Apps

50 m

20 m

I

I

I

I

0.01 0.1 1 10 100 1000

01

23

4

Exotic occurrences,Exotic occurrences,Montane uplandsMontane uplands

% e

xo

tic

of

tota

l sp

eci

es

oc

curr

enc

es

Area (m2)


Most frequent exotics:

Poa compressa

Microstegium vimineum

Rosa multiflora

Festuca ovina

Stellaria media

Exotic occurrences,Exotic occurrences,Piedmont uplandsPiedmont uplands

02

46

810

% e

xoti

c o

f to

tal

spec

ies

occ

urr

ence

s

0.01 0.1 1 10 100 1000 10000Area (m2)


Lonicerajaponica

Other upland exotics:

Ligustrum sinense

Celastrus orbiculata

Elaeagnus umbellata

Exotic Occurrence Across Scales

County State Nation0

51

01

52

0

% e

xo

tic

of

tota

l sp

eci

es

oc

curr

enc

es

% exotics in US (3138 / 18150)

Exotic Occurrence Across Scales

County State Nation0

51

01

52

0

% e

xo

tic

of

tota

l sp

eci

es

oc

curr

enc

es

Area (m2)

Agricultural borders

Montane riparian corridors

S App upland forests

0.01 0.1 1 10 100 1000

01

02

03

04

05

06

0

0.01 0.1 1 10 100 1000

01

02

03

04

05

06

0

0.01 0.1 1 10 100 1000

01

23

4

% exotics of species pool

% exotics in US (3138 / 18150)

Conclusions: Southeast US plant invasionsConclusions: Southeast US plant invasions

S App upland forests

HOTSPOTSHOTSPOTS: :

• uncommon relative to total land areauncommon relative to total land area

• exotics better dispersed at fine scalesexotics better dispersed at fine scales

• propagule pressure, disturbance, propagule pressure, disturbance, soil cationssoil cations

• no signal of biotic resistance no signal of biotic resistance

COLDSPOTS:

• relatively common—for now

• few exotic species; even rarer occurrences

• upland, shady, acidic, isolated

• biotic resistance or TIME?

• how long can cold spots stay cold?

Montane riparian corridors

Agricultural borders

-2 -1 0 1 2 3 4

0.0

0.2

0.4

0.6

0.8

1.0

Log10 Area (m2)

Per

cent

Tra

it C

lass

Vernal (March – early April)

Late Vernal(late April – June)

Summer(June - Sept)

Limiting Similarity – Phenology?Limiting Similarity – Phenology?

Flowering period

-2 -1 0 1 2 3 4

0.0

0.2

0.4

0.6

0.8

1.0

Log10 Area (m2)

Per

cent

Tra

it C

lass

-2 -1 0 1 2 3 4

0.0

0.2

0.4

0.6

0.8

1.0

Log10 Area (m2)

Per

cent

Tra

it C

lass



Summer(June - Sept)

Red maple!Red maple!


Flowering period

-2 -1 0 1 2 3 4

0.0

0.2

0.4

0.6

0.8

1.0

Log10 Area (m2)

Per

cent

Tra

it C

lass

-2 -1 0 1 2 3 4

0.0

0.2

0.4

0.6

0.8

1.0

Log10 Area (m2)

Per

cent

Tra

it C

lass



Summer(June - Sept)


Flowering period

Documents

Scale-dependent invasion patterns and community assembly in the Southeastern US flora