Community Ecology, Population Ecology, and Sustainability Chapter 6

Why Should We Care about the American Alligator? Overhunted Niches Ecosystem services Keystone species Endangered and threatened species Alligator farms Fig. 6-1, p. 108

Why Should We Care about the American Alligator? Fig. 6-1, p. 108

Community Structure and Species Diversity Physical appearance Edge effects Species diversity or richness Species abundance or evenness Niche structure

Natural Capital: Types, Sizes, and Stratification of Terrestrial Plants Tropical rain forest Coniferous forest Deciduous forest Thorn forest Thorn scrub Tall-grass prairie Short-grass prairie Desert scrub Fig. 6-2, p. 110

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

Tadpole develops into frog Life Cycle of a Frog Adult frog (3 years) Young frog sperm Tadpole develops into frog Sexual reproduction Tadpole Eggs Fertilized egg development Egg hatches Organ formation Fig. 6-3, p. 112

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

Why are Sharks Important? Ecological roles of sharks Shark misconceptions Human deaths and injuries Lightning is more dangerous than sharks Shark hunting and shark fins Mercury contamination Medical research Declining populations Hunting bans: effective?

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

Resource Partitioning and Niche Specialization Number of individuals Species 1 Species 2 Region of niche overlap Resource use Number of individuals Species 1 Species 2 Resource use Fig. 6-4, p. 114

Resource Partitioning of Warbler Species Fig. 6-5, p. 115

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

How Species Avoid Predators 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 Fig. 6-6, p. 116

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

Oxpeckers and black rhinoceros Clown fish and sea anemone Examples of Mutualism Oxpeckers and black rhinoceros Clown fish and sea anemone Mycorrhizae fungi on juniper seedlings in normal soil Lack of mycorrhizae fungi on juniper seedlings in sterilized soil Fig. 6-7, p. 117 © 2006 Brooks/Cole - Thomson

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

Primary Ecological Succession Lichens and mosses Exposed rocks Balsam fir, paper birch, and white spruce climax community Jack pine, black spruce, and aspen Heath mat Small herbs and shrubs Time Fig. 6-9, p. 119

Secondary Ecological Succession Mature oak-hickory forest Young pine forest with developing understory of oak and hickory trees Shrubs and pine seedlings Perennial weeds and grasses Annual weeds Time Fig. 6-10, p. 120

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

Population Growth Curves Environmental resistance Carrying capacity (K) Population size (N) Biotic potential Exponential growth Time (t) Fig. 6-11, p. 121

Logistic Growth of Sheep Population 2.0 Overshoot Carrying Capacity 1.5 Number of sheep (millions) 1.0 .5 1800 1825 1850 1875 1900 1925 Year Fig. 6-12, p. 121

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 Population Crash of Reindeer Overshoots Carrying Capacity 2,000 Population crashes 1,500 Number of sheep (millions) 1,000 Carrying capacity 500 1910 1920 1930 1940 1950 Year Fig. 6-13, p. 122

Reproductive Patterns r-selected species Opportunists (mostly r-selected) Environmental impacts on opportunists K-selected species (competitors) Intermediate and variable reproductive patterns

Positions of r-selected and K-selected Species on Population Growth Curve Carrying capacity K K species; experience K selection Number of individuals Number of individuals r species; experience r selection Time Fig. 6-14, p. 122

r-selected Opportunists and K-selected Species Fig. 6-15, p. 123

r-selected Opportunists and K-selected Species r-Selected Species r-selected Opportunists and K-selected Species Dandelion Cockroach 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 Elephant Saguaro 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 Fig. 6-15b, p. 123

Characteristics of Natural and Human-Dominated Systems Property Natural Systems Human-Dominated Systems Complexity Energy source Waste production Nutrients Net primary productivity Biologically diverse Renewable solar energy Little, if any Recycled Shared among many species Biologically simplified Mostly nonrenewable fossil fuel energy High Often lost of wasted Used, destroyed, or degraded to support human activities Fig. 6-16, p. 124

Human Impacts on Ecosystems Natural Capital Degradation Altering Nature to Meet Our Needs Reduction of biodiversity Increasing use of the earth's net primary productivity Increasing genetic resistance of pest species and disease causing bacteria Elimination of many natural predators Deliberate or accidental introduction of potentially harmful species into communities Using some renewable resources faster than they can be replenished Interfering with the earth's chemical cycling and energy flow processes Relying mostly on polluting fossil fuels Fig. 6-17, p. 125

Four Principles of Sustainability Solar Energy Population Control PRINCIPLES OF SUSTAINABILITY Nutrient Recycling Biodiversity Fig. 6-18, p. 126

Solutions: Implications of the Principles of Sustainability How Nature Works Lessons for Us Solutions: Implications of the Principles of Sustainability Runs on renewable solar energy. Recycles nutrients and wastes. There is little waste in nature. Uses biodiversity to maintain itself and adapt to new environmental conditions. Controls a species' population size and resource use by interactions with its environment and other species. Rely mostly on renewable solar energy. Prevent and reduce pollution and recycle and reuse resources. Preserve biodiversity by protecting ecosystem services and preventing premature extinction of species. Reduce births and wasteful resource use to prevent environmental overload and depletion and degradation of resources. Fig. 6-19, p. 126

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