Community Ecology, Population Ecology, And Sustainability

8/3/2019 Community Ecology, Population Ecology, And Sustainability

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Community Ecology, Population

Ecology, and Sustainability

Chapter 6



Key Concepts Factors determining number of species in a

community

Roles of species Species interactions

Responses to changes in environmental

conditions Reproductive patterns

Major impacts from humans

Sustainable living



Community Structure and Species

Diversity Physical appearance

Edge effects

Species diversity or richness

Species abundance or evenness

Niche structure



Fig. 6-2, p. 110

Natural Capital: Types, Sizes, and

Stratification of Terrestrial Plants

Tropicalrain forest

Coniferousforest

Deciduousforest

Thornforest

Thornscrub

Tall-grassprairie

Short-grassprairie

Desertscrub



Species Diversity and Ecological

Stability Many different species provide ecological stability

Some exceptions

Minimum threshold of species diversity

Many unknowns

Net primary productivity (NPP)

Essential and nonessential species



Types of Species Native

Nonnative (invasive or alien)

Indicator

Keystone

Foundation



Indicator Species Provide early warnings

Indicator of water quality

Birds as environmental indicators

Butterflies

Amphibians



Amphibians as Indicator Species

Environmentally sensitive life cycle

Vulnerable eggs and skin

Declining populations



sperm

Eggs

Sexualreproduction

Fertilized eggdevelopment Organ formation

Egg hatches

Tadpole

Tadpole develops intofrog

Young frogAdult frog(3 years)

Fig. 6-3, p. 112

Life Cycle of a Frog



Possible Causes of Declining

Amphibian Populations

Habitat loss and fragmentation

Prolonged drought

Pollution

Increases in ultraviolet radiation

Parasites

Overhunting

Disease

Nonnative species



Why Should We Care about

Vanishing Amphibians?

Indicator of environmental health

Important ecological roles of amphibians

Genetic storehouse for pharmaceuticals



Keystone Species

What is a keystone?

Keystone species play critical ecological roles

Pollination

Top predators

Dung beetles

Sharks



Foundation Species

Relationship to keystones species

Play important roles in shaping communities

Elephants

Contributions of bats and birds



Species Interactions Interspecific competition

Predation

Parasitism

Mutualism

Commensalism



Species Interactions: Competition

Interspecific Competition

Fundamental niches

Fighting for limited resources

Competition from humans



Reducing or Avoiding Competition

Resource partitioning

Role of natural selection

Specialization and sharing of resources

Resource partitioning of warblers

R P i i i d Ni h


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N u

m b e r o f i n d i v i d u a l s

N u m b e r o f i n d i v i d

u a l s

Resource use

Resource use

Species 1 Species 2

Region

ofniche overlap

Species 1 Species 2

Resource Partitioning and NicheSpecialization


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Resource Partitioning of Warbler

Species



Predator and Prey Interactions Carnivores and herbivores

Predators

Prey

Natural selection and prey populations



How Do Predators Increase Their

Chances of Getting a Meal? Speed

Senses

Camouflage and ambush

Chemical warfare (venom)



Avoiding and Defending Against

Predators Escape

Senses

Armor

Camouflage

Chemical warfare

Warning coloration

Mimicry

Behavior strategies

Safety in numbers



Span worm Bombardier beetle

Viceroy butterfly mimicsmonarch butterfly

Foul-tasting monarchbutterfly

Poison dart frog When touched, thesnake caterpillarchanges shape to looklike the head of a snake

Wandering leaf insect

Hind wings of io mothresemble eyes of amuch larger animal

Fig. 6-6, p. 116

How Species Avoid Predators



Parasites

Parasitism

Hosts

Inside or outside of hosts

Harmful effects on hosts

Important ecological roles of parasites



Mutualism

Both species benefit

Pollination

Benefits include nutrition and protection

Mycorrhizae

Gut inhabitant mutualism

E l f M li



Oxpeckers and black rhinoceros Clown fish and sea anemone

Lack of mycorrhizae fungi onjuniper seedlings in sterilized soil Fig. 6-7, p. 117

Examples of Mutualism

© 2006 Brooks/Cole - Thomson

Mycorrhizae fungi on juniperseedlings in normal soil



Commensalism Species interaction that benefits one

and has little or no effect on the other

Example: Small plants growing in

shade of larger plants

Epiphytes



Bromeliad Commensalism

Fig. 6-8, p. 118



Ecological Succession:

Communities in Transition

What is ecological succession?

Primary succession

Secondary succession

P i E l i l S i



Fig. 6-9, p. 119

Small herbsand shrubs

Heath mat

Jack pine,black spruce,

and aspen

Balsam fir, paper

birch, and whitespruce climaxcommunity

Exposedrocks

Lichensand mosses

Primary Ecological Succession

S d E l i l S i



Fig. 6-10, p. 120

Annualweeds

Perennialweeds and

grasses

Shrubsand pineseedlings

Young pine forest withdeveloping understory

of oak and hickorytrees

Mature oak-hickory forest

Secondary Ecological Succession



How Predictable is Succession?

Climax community concept

“Balance of nature”

New views of equilibrium in nature

Unpredictable succession

Natural struggles



Population Dynamics: Factors

Affecting Population Size

Population change = (births + immigration)

– (deaths + emigration)

Age structure (stages)

Age and population stability



Limits on Population Growth

Biotic potential

Intrinsic rate of increase ( r)

No indefinite population growth

Environmental resistance

Carrying capacity ( K )



Exponential and Logistic Population

Growth Resources control population growth

Exponential growth

Logistic growth



Fig. 6-11, p. 121

Carrying capacity (K )

Environmental

resistance

Bioticpotential

Exponentialgrowth

Population Growth Curves

Time (t )

P o p u l a t i o n s

i z e ( N )



Fig. 6-12, p. 121

Logistic Growth of Sheep Population

Overshoot Carrying Capacity

Year

N

u m b e r o f s h e e

p ( m i l l i o n s )

2.0

1.5

1.0

.5

1800 1825 1850 1875 1900 1925



When Population Size Exceeds

Carrying Capacity

Switch to new resources, move or die

Overshoots

Reproductive time lag

Population dieback or crash

Famines among humans

Factors controlling human carrying capacity

Exponential Growth Overshoot and



Exponential Growth, Overshoot and

Population Crash of Reindeer

Fig. 6-13, p. 122

PopulationOvershootsCarryingCapacity

Populationcrashes

Carrying

capacity

Year

N

u m b e r o f s h e e

p ( m i l l i o n s ) 2,000

1,500

1,000

500

01910 1920 1930 1940 1950



Reproductive Patterns

r-selected species

Opportunists (mostly r-selected)

Environmental impacts on opportunists

K-selected species (competitors)

Intermediate and variable reproductive patterns

P i i f l d d K l d S i



Carrying capacity

K species;experienceK selection

r species;

experiencer selection

K

Fig. 6-14, p. 122

Positions of r-selected and K-selected Species on

Population Growth Curve

Number of individuals

Time

N u

m b e r o f i n d i v i d u

a l s



Fig. 6-15, p. 123

r-selected Opportunists and K-selected Species

S l t d S i



r-Selected Species

Cockroach

Dandelion

Many small offspring

Little or no parental care and protection of offspring

Early reproductive age

Most offspring die before reaching reproductive age

Small adults

Adapted to unstable climate and environmental conditions

High population growth rate (r )

Population size fluctuates wildly above and below carrying capacity (K )

Generalist niche

Low ability to compete

Early successional species

Fig. 6-15a, p. 123

r-selected

Opportunists and

K-selected Species

K S l t d S i



Fewer, larger offspring

High parental care and protection of offspring

Later reproductive age

Most offspring survive to reproductive age

Larger adults

Adapted to stable climate and environmental conditions

Lower population growth rate (r )

Population size fairly stable and usually close to carrying capacity (K )

Specialist niche

High ability to compete

Late successional species

ElephantSaguaro

K-Selected Species

Fig. 6-15b, p. 123

r-selected

Opportunists and

K-selected Species

Characteristics of Natural and Human



Fig. 6-16, p. 124

Property Natural Systems Human-DominatedSystems

Complexity

Energy source

Waste production

Nutrients

Net primaryproductivity

Biologically diverse

Renewable solarenergy

Little, if any

Recycled

Shared among manyspecies

Biologicallysimplified

Mostly nonrenewablefossil fuel energy

High

Often lost of wasted

Used, destroyed, ordegraded to supporthuman activities

Characteristics of Natural and Human-

Dominated Systems

Human Impacts on Ecosystems



Fig. 6-17, p. 125

Reduction of biodiversity

Increasing use of the earth'snet primary productivity

Increasing genetic resistanceof pest species and diseasecausing bacteria

Elimination of many naturalpredators

Deliberate or accidentalintroduction of potentiallyharmful species intocommunities

Using some renewableresources faster than they canbe replenished

Interfering with the earth'schemical cycling and energyflow processes

Relying mostly on polluting

fossil fuels

Human Impacts on EcosystemsNatural Capital Degradation

Altering Nature to Meet Our Needs

Four Principles of Sustainability



Fig. 6-18, p. 126

Four Principles of Sustainability

PRINCIPLESOF

SUSTAINABILITY

Solutions



Runs onrenewablesolar energy.

Recyclesnutrientsand wastes.There is littlewastein nature.

Uses biodiversityto maintain itselfand adapt to newenvironmentalconditions.

Controls aspecies'population size

and resource useby interactionswith itsenvironmentand otherspecies.

Rely mostly onrenewable solarenergy.

Prevent andreducepollution andrecycleand reuseresources.

Preservebiodiversityby protectingecosystemservices andpreventingprematureextinctionof species.

Reduce birthsandwasteful resourceuse to preventenvironmentaloverload anddepletion anddegradation ofresources.

Fig. 6-19, p. 126

Solutions: Implications of the Principles

of Sustainability

Principles of Sustainability

How Nature Works Lessons for Us



Lessons from Nature We are dependent on the Earth and Sun

Everything is interdependent with everything else

We can never do just one thing

Earth’s natural capital must be sustained

Precautionary Principle

Prevention is better than cure

Risks must be taken



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Community Ecology, Population Ecology, And Sustainability

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