Community structure, succession

What is Community Structure? Physical appearance

Relative sizes, stratification, and distribution of its populations and species.

Species diversity and richness The number of different species

Species abundance The number of individuals of each species

Niche structure The number of ecological niches, their resemblance,

and how they interact

m ft

10

50

20

30

100

Tropical rain forest

Coniferous forest

Deciduous forest

Thorn forest

Tall-grass prairie

Short-grass prairie

Desert scrub

Thorn scrub

Types, sizes, and stratification of plant species in terrestrial

communities

Mosaic of vegatation patches

•Ecotones – transition zones

between ecosystems

•Edge Effects - differences in

the physical structure and

physical properties between

two ecosystems

•Riparian Zone- the thin strip

or patch of vegetation

surrounding a stream.

Important habitat/resource

areas

Species Diversity Most Species Rich Environments

Major factors affecting species diversity

Tropical Rainforest

Coral Reefs

The deep sea

Large Tropical Lake

Latitude

Depth

Pollution

10

Sp

eci

es

Div

ers

ity

1,000

100

Latitude

80ºN 60 40 20 0

Sp

eci

es

Div

ers

ity

200

100

0

90ºN 60 30 0 30ºS 60

Latitude

latitudinal species diversity gradient

0 0

Sp

eci

es

div

ers

ity

25

20

15

5

10

0 2,000 4,000 6,000

Depth (meters)

2,000 4,000 6,000

Depth (meters)

25

20

15

5

10

0

Coast Deep Sea Coast Deep Sea

Snails Tube worms

Depth

Number of individuals per diatom species

Nu

mb

er

of

dia

tom

sp

eci

es

Unpolluted stream

Polluted stream

Pollution

What determines the number of

species in an isolated ecosystem?

Island Ecosystems

Size of the ecosystem

Degree of isolation

Species Equilibrium Model or

Theory of Island Biogeography (MacArthur and Wilson)

Number of species found on an island determined by balance between:

Rate of immigration

Rate of extinction

Immigration and extinction rates effected by:

Size of island

Distance from nearest mainland

High

Low

Ra

te o

f im

mig

rati

on

o

r e

xti

nct

ion

Immigration and extinction rates

Number of species on island

(a)

© 2004 Brooks/Cole – Thomson Learning

Equlibrium point

High

Low

Ra

te o

f im

mig

rati

on

o

r e

xti

nct

ion

Small island

Effect of island size

Number of species on island

(b)

Large island

High

Low

Ra

te o

f im

mig

rati

on

o

r e

xti

nct

ion

Far island

Effect of distance from mainland

Number of species on island

(c)

Near island

© 2004 Brooks/Cole – Thomson Learning

100

50

25

12.5

6.25

0 2,000 4,000 6,000 8,000 10,000

Distance from New Guinea (kilometers)

Nu

mb

er

of

spe

cie

s (p

erc

en

tag

e o

f sa

mp

le s

tud

ied

)

NEW GUINEA

© 20

04

Bro

ok

s/Co

le –

Th

om

son

Le

arn

ing

Species diversity decreases with increasing distance

100

1 10 100 1,000 10,000 100,000

Area (square miles)

Nu

mb

er

of

am

ph

ibia

n a

nd

re

pti

le s

pe

cie

s

10

SABA MONTSERRAT CUBA

Hispaniola

Puerto Rico

Jamaica

Cuba

Montserrat

Saba

Redonda

© 20

04

Bro

ok

s/Co

le –

Th

om

son

Le

arn

ing

Species diversity increases with increasing island size

Roles of Species in Ecosystems

native

non-native

indicator

Keystone

Foundation

Native and Non-native Species Native species

Species that normally live and thrive in a

particular ecosystem

Non-native (exotic or alien) species

Species that migrate into an ecosystem or are

deliberately or accidentally introduced into an

ecosystem

Cane toads

Feral Hogs

Indicator Species Species that serve as early warning of damage

to a community or an ecosystem (most

sensitive)

Birds

Fish

Amphibians

Habitat

loss/degradation

Drought

Pollution

UV radiation

Parasitism

Over-hunting

Diseases

Immigration or

introduction of

predators or

competitors

sperm

Eggs

Sexual reproduction

Fertilized egg development

Organ formation

Egg hatches

Tadpole

Tadpole develops Into frog

Young frog

Adult frog (3 years)

Indicators of things like . .

Keystone Species Species that play roles affecting many other

organisms in an ecosystem Strong interaction with other species affect health and

survival of species

Process material out of proportion to their numbers or biomass

Pollination

Seed dispersion

Habitat modification

Predation by top carnivores

Recycling of plant and animal waste

Example: American Alligator

Foundation Species Species that play a major role in shaping their

communities by creating and enhancing their habitats in ways that benefit other species.

Elephants—create openings in woodlands

Beaver- build dams to create ponds and wetlands

Fruit bats—deposit seeds in droppings to help regenerate forests

What is the major difference between Foundation and Keystone species?

Species Interactions competition

predation

parasitism

mutualism

commensalism

Competition Intraspecific competition – competition between

members of the same species

Gain a competitive advantage (Plants)

Chemical inhibitors

Seed dispersal

Territoriality (Animals)

Patrol or mark an area

Defend an area

Competition Interspecific competition – competition

between members of two or more different

species

Abundant commonly used resources (food,

sunlight, water, soil nutrients, space, nesting

sites)

Fundamental niche

Limited resources

Overlap of fundamental niches

Interspecific Competition Interference competition

One species limits another’s access to some

resources

Exploitation competition

Competing species have equal access to

resources but differ in how fast or efficiently they

exploit it

Competitive Exclusion Principle

The niches of two species cannot overlap completely or significantly for very long.

Nu

mb

er

of

ind

ivid

ua

ls

Nu

mb

er

of

ind

ivid

ua

ls

Resource use

Resource use

Species 1 Species 2

Region of

niche overlap

Species 1 Species 2

Resource Partitioning

Niche Specialization

Resource Partitioning

Each species minimizes competition with the others for food by spending at least half its feeding time in a distinct portion of the spruce tree and by consuming somewhat different insect species.

Predator – Prey Relationship Predation – members of one species (predator)

feed directly on all or part of a living organism of another species (prey).

Benefits from reducing prey population

Gives remaining prey greater access to food supply

Can improve the genetic stocks of the prey population

Predator Tactics Pursuit vs….

Pursuit: Cheetah, wolves,eagles.

Ambush: owls, preying mantis, humans

Ambush

Prey Tactics Run, swim, or fly fast

Highly developed

sense of sight or

smell

Protective shells

Thick bark

Spines or thorns

Chemical defenses

Camouflage

Warning coloration

Mimicry

Behavioral strategies

Span worm Bombardier beetle

Viceroy butterfly Mimics monarch butterfly

Foul-tasting monarch butterfly

Poison dart frog

When touched, the snake caterpillar changes shape to look like the head of a snake

Wandering leaf insect

Hind wings of io Moth resemble eyes of a much larger animal

Symbiotic Species Interactions Symbiosis – relationship in which species live

together in an intimate association.

Parasitism

Mutualism

Commensalism

Parasitism One species (parasite) feeds on part of another

organism (host) by living on or in the host.

Smaller than the host

Remains closely associated with host and may

weaken host over time

Rarely kills its host

Mutualism Two species interact in ways that benefit both

Nutritional mutualism

Pollination, lichens, rhizobium, coral, bacteria

Nutrition and protection

Birds and large animals, clownfish and anemones,

mycorrihizae and plants

Figure 8-12 Page 179

Oxpeckers and black rhinoceros Clown fish and sea anemone

Lack of mycorrhizae fungi on juniper seedlings in normal soil

Mycorrhizae fungi on juniper seedlings in sterilized soil

Commensalism

symbiotic

relationship that

benefits one

species but

neither harms nor

helps the other

species

Ecological Succession - the gradual change in species composition in a

given area

Primary Succession – gradual establishment of biotic communities on nearly lifeless ground

Secondary Succession – reestablishment of biotic communities in an area where some type of biotic community is already present

Small herbs and shrubs

Heath mat

Jack pine, black spruce,

and aspen

Balsam fir, paper birch, and

white spruce climax community

Time

Exposed rocks

Lichens and mosses

Primary Ecological

Succession

Pioneer

species

Early

successional

Mid-

successional

Late

Successional or

Climax

Community

Time Annual weeds

Perennial weeds and

grasses

Shrubs Young pine forest

Mature oak-hickory forest

Secondary

Ecological

Succession

Midsuccessional

Species

Elk

Moose

Deer

Ruffled grouse

Snowshoe hare

Bluebird

Late Successional

Species

Turkey

Martin

Hammond’s

flycatcher

Gray squirrel

Wilderness

Species

Grizzly bear

Wolf

Caribou

Bighorn sheep

California condor

Great horned owl

Early Successional

Species

Rabbit

Quail

Ringneck pheasant

Dove

Bobolink

Pocket gopher

Ecological succession

© 2004 Brooks/Cole – Thomson Learning

Ecological Succession of Wildlife

Species

Changes Affecting Ecosystems Catastrophic

Natural Drought

Flood

Fire

Volcanic eruption

Earthquake

Hurricane

Landslide

Disease

Human-caused Deforestation

Overgrazing

Plowing

Erosion

Pesticide application

Fire

Mining

Urbanization

Water and air pollution

Loss and degradation of wildlife habitat

Gradual

Natural Climate change

Immigration

Adaptation and evolution

Ecological succession

Disease

Human-caused Salinization

Soil compaction

Groundwater depletion

Water and air pollution

Loss and degradation of wildlife habitat

Introduction of nonnative species

Overhunting and overfishing

Toxic contamination

Urbanization

Excessive tourism

Predictability and the

Balance of Nature Old Concept

Succession

Climax Community

New Concept

Biotic change

Mature community or

vegetative patches

100 0

Percentage disturbance

Sp

ec

ies

div

ers

ity

Intermediate

disturbance

hypothesis

Stability – the ability of living systems to

withstand or recover from externally

imposed changes or stresses.

Inertia – ability to resist being disturbed

Constancy – keep numbers within limits

Resilience – ability to bounce back

Precautionary Principle When evidence indicates an activity can harm

human health or the environment, we should take precautionary measures to prevent harm even if some of the cause-and-effect relationships have not been fully established scientifically.

Grizzly bear

NORTH AMERICA

Spotted owl

Black- footed ferret

Kemp’s ridley turtle

California condor

Golden toad

Columbia has lost one-third of its forest

Black lion tamarin

SOUTH AMERICA

More than 60% of the Pacific Northwest coastal forest has been cut down

40% of North America’s range and cropland has lost productivity

Hawaiian monk seal

Half of the forest in Honduras and Nicaragua has disappeared

Mangroves cleared in Equador for shrimp ponds

Southern Chile’s rain forest is threatened

Little of Brazil’s Atlantic forest remains

Every year 14,000 square kilometers of rain forest is destroyed in the Amazon Basin

Coral reef destruction

Much of Everglades National Park has dried out and lost 90% of its wading birds

ATLANTIC OCEAN

PACIFIC OCEAN

Manatee

Chesapeake Bay is overfished and polluted

Fish catch in the north-west Atlantic has fallen 42% since its peak in 1973

Humpback whale

St. Lawrence beluga whale Eastern

cougar

Florida panther

Environmental degradation

Vanishing biodiversity

Endangered species

EUROPE

Mediterranean

Liberia

AFRICA

Imperial eagle

640,000 square kilometers south of the Sahara have turned to desert since 1940

Mali

Burkina Faso

Sierra Leone

Togo Sao Tome

68% of the Congo’s rain forest is slated for cleaning

Fish catches in Southeast Atlantic have dropped by more than 50% since 1973 Black

rhinoceros

Zambia

Angola

Congo Rwanda Burundi

Uganda Somalia

Nigeria

Chad Niger Benin Golden

tamarin

Ethiopia

Eritrea

Madagascar has lost 66% of its tropical forest

Aye-aye

Yemen Oman

Saudi Arabia

Poland is one of the world’s most polluted countries

Many parts of former Soviet Union are polluted with industrial and radio- active waste

Area of Aral Sea has Shrunk 46%

Central Asia from the Middle East to China has lost 72% of range and cropland

ASIA

Asian elephant

India and Sri Lanka have almost no rain forest left

In peninsular Malaysia almost all forests have been cut

INDIAN OCEAN

Indonesia’s coral reefs are threatened and mangrove forests have been cut in half

Giant panda

Kouprey

Queen Alexandra’s Birdwing butterfly

Nail-tailed wallaby

AUSTALIA

Much of Australia’s range and cropland have turned to desert

90% of the coral reefs are threatened in the Philippines. All virgin forest will be gone by 2010

Deforestation in the Himalaya causes flooding in Bangladesh

Japanese timber imports are responsible for much of the world’s tropical deforestation

Blue whale

ANTARCTICA

A thinning of the ozone layer occurs over Antarctica during summer

Snow leopard

6.0 or more children per woman

Species Diversity Two factors define species diversity:

Species Richness

Number of species in the community.

Species Evenness

Relative abundance of species.

Species Diversity

Environmental Complexity In general, species diversity increases with

environmental complexity or heterogeneity.

Many studies have shown positive relationship between environmental complexity and species diversity.

Environmental Complexity

Quantitative Index of Species Diversity Shannon Wiener Index:

s

H’ = -∑pi logepi

i=l

H’ = Value of SW diversity index.

pi = Proportion of the ith species.

loge = Natural logarithm of pi.

s = Number of species in community.