2. Community Ecology Issues
What factors are most significant in structuring a
community?
What factors are the most significant in determining
its species composition?
What happens to a community when a species is
lost?
What happens to a community when a species is
introduced by humans?
3. Individualistic Hypothesis
Chance assemblage of
different species in a
particular area because
of similar abiotic
requirements
Emphasizes studying
single species as the
essential units for the
interrelationships and
distributions of organisms Indonesian reefs have the greatest species richness
Predicts that communities with over 1650 known species.
should lack discrete
geographic boundaries
4. Interactive Hypothesis
Closely linked species, locked
into association by
mandatory biotic interactions
Views communities as
superorganism.
Predicts that species should
be clustered into discrete
communities with noticeable
boundaries Pando (or The Trembling Giant) is a clonal colony
of a single male Quaking Aspen (Populus
Presence or absence is
tremuloides) tree located in the U.S. state of Utah,
governed by other species in all determined to be part of a single living organism
by identical genetic markers and one massive
group underground root system. he root system of Pando
is claimed by some to be among the oldest known
living organisms in existence at 80,000 years of age
5. Community Organization – Bottom-Up Model
Nutrients control Plants control
Minerals control plant types and herbivores, which
community number, act as in turn control
organization limiting factors predators
*Changes in this community are done by adding or removing
minerals
6. Trophic Cascade Model (top down model)
Plants uptake
Predators control Herbivores regulate minerals and make
herbivores, apex undergrowth and them available to
consumers, also
predators other plants
recycle them.
9. Community Variables
Physical Appearance
Types of Species
Number of Species
Ecological Niches
10. 100
Plant Species
30
Stratification
20
•Relative Size of Populations
•Stratification of Populations
50
•Distribution of Populations
10
ft m
Tropical Coniferous Deciduous Thorn Thorn Tall-grass Short-grass Desert
rain forest forest forest forest scrub prairie prairie scrub
•Communities are patchy
•Communities do not have defined boundaries
•Increased edges make species more vulnerable to stresses
11. Types of Species
Species Richness (number of different species)
Species Evenness (population size)
Niche Structure (number of niches)
12. Niches
Fundamental
Niche
Determined by
abiotic factors
Realized Niche
Determined by
species
competition
14. Rich Environments Have Low Species Evenness
Tropical Rain Forests
Coral Reefs
The Deep Sea
Large Tropical Lakes
15. Richness Variables
Latitude
Pollution
Habitat Diversity
Net Primary Productivity (NPP)
Habitat Disturbance
Time
16. 1,000
200
Species Diversity
Species Diversity
100
100
10
0
80ºN 60 40 20 0
90ºN 60 30 0 30ºS 60
Latitude Latitude
Changes in Species Diversity by Latitude
What do these graphs say about an organisms “range of tolerance”?
27. Factors that Influence Island Communities
Degree of isolation (distance to nearest neighbor, and mainland)
Length of isolation (time)
Size of island (larger area usually facilitates greater diversity)
Climate (tropical versus arctic, humid versus arid, etc.)
Location relative to ocean currents (influences nutrient, fish, bird, and
seed flow patterns)
Initial plant and animal composition if previously attached to a
larger land mass (e.g., marsupials, primates, etc.)
The species composition of earliest arrivals (if always isolated)
Serendipity (the impacts of chance arrivals)
Human activity
32. Parks Dilemma
Reserves and national parks form islands inside
human-altered landscapes (habitat fragmentation).
Reserves could lose species as they 'relaxed
towards equilibrium' (that is they would lose species
as they achieved their new equilibrium number,
known as ecosystem decay).
This is particularly true when conserving larger
species which tend to have larger ranges.
34. Allopatric vs. Sympatric Speciation
Allopatric Speciation is where new gene pools arise
out of natural selection in isolated gene pools
(multiregional hypothesis)
Sympatric Speciation, the idea of different species
arising from one ancestral species in the same area.
(single-origin hypothesis)
Interbreeding between the two differently adapted
species would prevent speciation.
36. Indicator Species of the World
Trout need clean water with high dissolved oxygen
Birds and butterflies are susceptible to habitat
fragmentation and chemical pesticides
Plants can be genetically engineered to detect high level
of soil nitrates used in explosives
Frogs are an indicator species which eat insect eggs that
have no protection from UV radiation or pollution
38. Gray Treefrog –
Hyla versicolor
Commonly found in the
NE United States.
Reports about the
decline of frogs and
toads in pristine
environments such as
nature reserves and
parks
greatly concerns
ecologists who look at
amphibians as an
indicator species,
warning of
environmental stress.
39. Warnings from Frogs
Habitat Loss and Fragmentation
Pollution
Increases in UV Radiation
Over Hunting
Parasitism
Disease
Non-native Predators
40. Ecological Role of Frogs
Indicators that environmental quality is deteriorating
They consume more insects than birds
Represent a storehouse of pharmaceutical products
43. Role of a Keystone Species
Crucial in determining the nature and structure of an
ecosystem.
Usually affect the available amount of food, water, or
some other resource.
Usually not the most abundant species in an ecosystem.
Are the chief concern of conservation biologists.
Test for a keystone species through “removal
experiments”.
Loss of keystone species cause tropic cascades.
44. Example of Keystone Species
Bees Lion
Humming Birds Alligator Frogs
Bats Dung Beetle
Great White Sharks Sea Stars
Leopard
Sea Otters
45. Activity: Movie
Watch the National
Geographic movie “The
Wolves of Yellowstone”
Write an essay
explaining the role of
wolves in the northern
coniferous forests.
47. Foundation Species Examples
Elephants push over grass or uproot trees
Mussels provide homes to invertebrate species that
do not do well in the presence of mussel
competitors, such as the sea star
Foundation Species create
and enhance habitats for
other organisms.
59. Benefits of Predation
Weeds out sick, weak, and aged
Gives remaining prey better access to food supplies
Prevents excessive population growth, which can result in
crashes
Helps successive genetic traits to become more dominant
(directional natural selection)
Can enhance the reproductive success and long-term
survival of the prey species (adaptive evolution)
89. Oxpeckers and black rhinoceros Clown fish and sea anemone
Mycorrhizae fungi on juniper Lack of mycorrhizae fungi on
seedlings in normal soil juniper seedlings in sterilized soil
90.
91. Mutualism Extras
Sometimes require the coevolution of adaptations in
both participating species
Changes in one species are likely to affect the
survival and reproduction of the other
Many mutualistic relationships may have evolved
from predator-prey or host-parasite interactions.
98. Characteristics of Pioneer Species
Short-lived and reproduce frequently
Number can great.
Can withstand the lack of moisture
Can withstand extreme temperatures
Involved in soil formation
Secrete acids that break down rocks
Stabilizing nutrient cycle
99. Exposed Lichens
rocks and mosses
Balsam fir,
paper birch, and
white spruce
Jack pine,
climax community
black spruce,
and aspen
Heath mat
Small herbs
and shrubs
Time
100. Characteristics of Early Successional Plant Species
Grow close to the ground
Do not require established nutrient cycles
Can established large populations quickly
Have short lives
101. Ecosystem Structure During Early Succesional
Stage
Plant Size Small
Species Diversity Low
Trophic Structure Mostly producers, few
decomposers
Ecological Niches
Few, mostly
Community
generalized
Organization
Low
102. HOW DO SPECIES REPLACE
ONE ANOTHER IN
ECOLOGICAL
SUCCESSION?
106. Disturbances
Fire
Drought
Flooding
Mining
Clear-Cutting a Forest
Plowing a Grassland
Applying Pesticides
Climate Change
Invasion of Exotic
Yellowstone Park Forest Fire 1988.
Species
111. Mature Communities
High occurrence of vegetation patches
Contain large plants
High species diversity
Well-established, efficient nutrient cycles
Many, specialized niches
High biomass
Low NPP
Low Immigration / Emigration Rate
Complex food webs dominated by decomposers
Efficient use of energy
113. Precautionary Principle
Monitor cause and effect relationships
Complete risk analysis studies before beginning
Take acceptable risks to learn
Complete independent reviews of our actions
114. Research Helps Us to Evaluate Environmental Issues
Agricultural Landscapes
National Parks
Reservoirs
Marine Fisheries
115. Grizzly
bear
St. Lawrence
NORTH
beluga whale
AMERICA Eastern Humpback
More than 60% of the cougar whale
Pacific Northwest Spotted
coastal forest has
owl
been cut down Fish catch in the north-west Atlantic has fallen
Black- 42% since its peak in 1973
40% of North America’s footed Florida
Chesapeake Bay is overfished and polluted
ferret panther
range and cropland
has lost productivity California Manatee
Kemp’s
condor Much of Everglades National Park has dried out
ridley
and lost 90% of its wading birds
Hawaiian turtle
monk seal Golden Coral reef destruction
Half of the forest toad
in Honduras and
Nicaragua has Every year 14,000
Columbia has
disappeared square kilometers of
lost one-third of
rain forest is destroyed
its forest
Mangroves
in the Amazon Basin
cleared
in Equador for
shrimp ponds
Black lion
tamarin
PACIFIC
SOUTH
OCEAN Little of Brazil’s
AMERICA Atlantic forest ATLANTIC
remains
OCEAN
Environmental degradation Southern
Chile’s rain
forest is
threatened
Vanishing biodiversity
Endangered species
6.0 or more children
per woman
116. Many parts of
former Soviet Union ASIA
are polluted with
Poland is one of industrial and radio-
the world’s most active waste Central Asia from the
polluted countries
Middle East to China
has lost 72% of range Giant
Imperial eagle and cropland panda
EUROPE Japanese timber imports
are responsible for much
Area of
of the world’s tropical
Snow leopard
Aral Sea has
deforestation
Shrunk 46%
Mediterranean
640,000 square kilometers Saudi
south of the Sahara have Arabia Deforestation in the Himalaya
Asian
turned to desert since 1940
causes flooding in Bangladesh
Liberia elephant
Oman Kouprey
Eritrea
Mali AFRICA Yemen 90% of the coral reefs
India and are threatened in the
Burkina Niger Ethiopia Sri Lanka Philippines. All virgin
Faso Benin Chad Golden have almost forest will be gone
Sierra tamarin no rain
Nigeria by 2010
Leone forest left
Togo Congo Uganda
Sao Tome Rwanda Somalia
In peninsular Malaysia Queen Alexandra’s
68% of the Burundi
almost all forests have
Congo’s Birdwing butterfly
Angola been cut
rain forest Indonesia’s
is slated Zambia coral reefs are Nail-tailed
for cleaning INDIAN OCEAN threatened
wallaby
and
Aye-aye
Fish catches in
mangrove AUSTALIA
Black
Southeast Atlantic
forests
have dropped by more rhinoceros Madagascar has
Much of
have been
lost 66% of its
than 50% since 1973
Australia’s
cut in half
tropical forest
range and
cropland
have turned
to desert
A thinning of the ozone layer occurs
Blue whale
over Antarctica during summer
ANTARCTICA