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
Pin
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