Relative abundance I: commonness and rarity

Bio 415/615

Questions

1. How does a rank abundance distribution quantify commonness and rarity?

2. What are the three components of the rarity scheme of Rabinowitz?

3. What are three ecological processes that lead to rarity?

4. Why might you manage rare species like chestnut and Venus flytrap differently?

889 oak trees, 100 bay trees, 10 maple trees, 1 birch tree

1 2 3 4Rank by abundance

% o

f in

divi

dual

s

100

10

1

.1

.01

Recall rank-abundance distributions (RADs)

Length of the line changes with diversity

Slope generally changes with diversity

Slope changes because of the change in evenness that generally correlates with system diversity

What would the slope be in a perfectly even community?

What influences dominance or non-equitability?

• Conditions that promote competitive suppression

– Low disturbance, abundant resources

• Conditions that deny species membership due to harsh conditions (‘stress’)

– allow ‘specialists’ to dominate

Grime’s model

J.P. Grime 1979

‘‘hump-backed model’ of local diversityhump-backed model’ of local diversity

Standing biomass (sometimes productivity)

Spec

ies

richn

ess

1. Dominance (competition)

2. Stress = reduces potential production

3. Disturbance = removes biomass

4. Local heterogeneity

5. Species pool size (how many potential colonists?)

What influences dominance or non-equitability?

RADs: Disturbance, succession

Bazzaz 1975

Ric

h c

oves

Red o

ak

Pin

e f

ore

st

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e h

eath

Spru

ce-

rhodo

Fir

Heath

Rich, mesic Dry or cold

Whittaker 1965

Geometric (logseries)

lognormal

GEOGRAPHIC RANGE

LARGE SMALL

HABITAT SPECIFICITY

WIDE NARROW WIDE NARROW

LOCAL POP. SIZE

LARGE, DOMINANT SOMEWHERE

Locally abundant over a large range in several habitats

(Common)

Locally abundant over a large range in a specific habitat

(Predictable)

Locally abundant in several habitats but restricted geographically

(Unlikely)

Locally abundant in a specific habitat but restricted geographically

(Endemic)

SMALL, NON-DOMINANT

Constantly sparse over a large range and in several habitats

(Sparse)

Constantly sparse in a specific habitat but over a large range

(Predictable)

Constantly sparse and geographically restricted in several habitats

(Non-existent?)

Constantly sparse and geographically restricted in a specific habitat

(Endemic)

7 Forms of Rarity based on three characteristics: geographic range, habitat specificity, and local population size (Rabinowitz 1981)

GEOGRAPHIC RANGE

LARGE SMALL

HABITAT SPECIFICITY

WIDE NARROW WIDE NARROW

LOCAL POP. SIZE

LARGE, DOMINANT SOMEWHERE

Locally abundant over a large range in several habitats

(Common)

Locally abundant over a large range in a specific habitat

(Predictable)

Locally abundant in several habitats but restricted geographically

(Unlikely)

Locally abundant in a specific habitat but restricted geographically

(Endemic)

SMALL, NON-DOMINANT

Constantly sparse over a large range and in several habitats

(Sparse)

Constantly sparse in a specific habitat but over a large range

(Predictable)

Constantly sparse and geographically restricted in several habitats

(Non-existent?)

Constantly sparse and geographically restricted in a specific habitat

(Endemic)

7 Forms of Rarity based on three characteristics: geographic range, habitat specificity, and local population size (Rabinowitz 1981)

GEOGRAPHIC RANGE

LARGE SMALL

HABITAT SPECIFICITY

WIDE NARROW WIDE NARROW

LOCAL POP. SIZE

LARGE, DOMINANT SOMEWHERE

SMALL, NON-DOMINANT

Rarity in the British Flora (Rabinowitz et al.); 39% no component of rarity3 kinds of rarity; evidence they are independent59% Narrow Habitat; 15% Small Range; 7% Small Population

Causes of Rarity—Natural Ecological, innate:• Innate biology, Narrow niche, rarity of

conditions, climate change• High trophic level species• Vulnerability to natural biological change• Disease, herbivory, predation, mutualism

Historical:• Poor dispersal relative to habitat dispersion,

historical limits, climate change• Recently evolved

Causes of Rarity—Imposed

1. Vulnerability to loss of dynamic process: fire, flood, beaver, disease, herbivory, predation – Increase of white-tailed deer, Loss of

panther, elk2. Sensitive to chemical, physical changes3. Found in human-exploited habitats4. Exploited species5. Area & isolation sensitive species

Pseudo-rarity

• Global scale is not the only scale at which populations are managed:– Nations– States– Counties / Cities– Parks

• Why are species rareat these smaller scales?

Geum triflorum, ‘prairie smoke’

Pseudo-rarity

• Global scale is not the only scale at which populations are managed:– Nations– States– Counties / Cities– Parks

• Why are species rareat these smaller scales?

Geum triflorum, ‘prairie smoke’

Pseudo-rarity

• Global scale is not the only scale at which populations are managed:– Nations– States– Counties / Cities– Parks

• Why are species rareat these smaller scales?

Geum triflorum, ‘prairie smoke’

Intrinsic Extinction Vulnerability

Local endemics: small range, habitat narrow, island species

Small population sizeLarge area needs

Large body size-large home range-high trophic level

Species of productive habitats used by peopleMigratory speciesHighly concentrated populations for breedingLimited dispersal abilityLow population growth rateLow genetic variationHigh dependence on species that are extinction

vulnerable

Types of rarity: American chestnut

• One of the most common, dominant trees of the eastern US before disease introduction

• NOW: still widespread but only in small shrub form

Large range, locally rare

Endothia parasitica -- Chestnut blight

A Chinese fungus

Chestnut

Range collapse of American chestnut after the introduction of chestnut blight

Many species were associated with chestnut, so many species participated in the “recovery”

Nonetheless:

Loss of consistent hard mast

Lower carrying capacity for wildlife

like black bears

7 species of butterflies extinct

Possibly other insects

(Butterflies are conspicuous and better known that other

groups)

Types of rarity: Venus Fly Trap, Dionaea muscipula

Endemic (locally

abundant)

"The fairest bloom the mountain knows Is not an iris or a wild rose But the little flower of which I'll tell Known as the brave acony bell.” From "Acony Bell", by Gillian Welch and David Rawlings

Oconee Bell -- Shortia galacifolia

Endemic (locally

abundant)

The story of Shortia1788, December 9 & 11—Collected by Michaux

He called it “a new plant” in his journal from

“les hautes montaignes de Caroline”

1839—Unnamed & undescribed specimen discovered

by Asa Gray in the Paris Herbarium

Gray named it for Dr. Charles Short

Gray searched on 3 occasions

1877—Rediscovered on Catawba River near Marion, NC

by George M. Hyams (89 years since discovery!)

1886—C. S. Sargent found original local (Keowee River)

using Michaux journal

Shortia galacifolia

Types of rarity: Rugelia nudicaulis

Endemic (locally

abundant)

Torreya taxifolia

Endemic (rare)

Types of rarity: yellowwood

Sparse

Types of rarity: baldcypress

Predictable

(specialist)

Types of rarity: Fraser fir

Specialist

endemic