Community Ecology, Population Ecology, and Sustainability Chapter 6

Why Should We Care about the American Alligator? Overhunted Overhunted Niches Niches Ecosystem services- gator holes, mounds, predation, clear vegetation… Ecosystem services- gator holes, mounds, predation, clear vegetation… Keystone species Keystone species Endangered and threatened species Endangered and threatened species Alligator farms Alligator farms Fig. 6-1, p. 108

Key Concepts Factors determining number of species in a community Factors determining number of species in a community Roles of species Roles of species Species interactions Species interactions Responses to changes in environmental conditions Responses to changes in environmental conditions Reproductive patterns Reproductive patterns Major impacts from humans Major impacts from humans Sustainable living Sustainable living

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

Species Diversity and Ecological Stability  Many different species provide ecological stability  Some exceptions  Minimum threshold of species diversity ( producer species?)  Many unknowns  Net primary productivity (NPP)  Essential and nonessential species

Species diversity by latitude Animation

Types of Species  Native  Nonnative (invasive or alien)  Indicator-  Keystone -  Foundation

Indicator Species  Provide early warnings of ecosystem damage  Indicator of water quality (trout)  Birds as environmental indicators (affected by habitat loss, chemicals)  Butterflies  Amphibians

Amphibians as Indicator Species  Environmentally sensitive life cycle  Vulnerable eggs and skin - susceptible to UV, chemicals  Declining populations- 25% extinct or vulnerable - why?

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

Possible Causes of Declining Amphibian Populations  Habitat loss and fragmentation (wetland loss, deforestation,…)  Prolonged drought  Pollution  Increases in ultraviolet radiation  Parasites  Overhunting - frog legs anyone?  Disease  Nonnative species - predators & competitors

Why Should We Care about Vanishing Amphibians?  Indicator of environmental health  Important ecological roles of amphibians (insect control)  Genetic storehouse for pharmaceuticals (painkillers, antibiotics, burn & heart disease medicines)

Keystone Species  What is a keystone?  Keystone species play critical ecological roles a. Pollination b. Top predators c. decomposition  EXAMPLES: Dung beetles, Sharks, bees, bats, wolves, alligators,

Why are Sharks Important?  Ecological roles of sharks  Shark misconceptions  Human deaths and injuries ( p. 113)- (sharks kill 7 people /yr globally)  Lightning is more dangerous than sharks  Shark hunting and shark fins ($10K for a shark fin???)  Mercury contamination  Medical research  Declining populations- (90 of 370 species endangered or threatened)  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  Symbiosis = close long term association 2 or more species A. Parasitism + - B. Mutualism + + C.Commensalism + 0

Types of two species interactions animation. Animation

Animation Gause's competition experiment interaction

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

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

Life history patterns interaction. Animation

Capture-recapture method interaction. Animation

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 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 How Species Avoid Predators “ If it is small and strikingly beautiful, it is probably poisonous. If it is strikingly beautiful and easy to catch, it is probably deadly. ” - E.O Wilson camouflage Chemical warfare / Warning mimicry Deceptive behavior

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 - fungi that helps plants extract nutrients and water from soil  Gut inhabitant mutualism

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

Commensalism + 0  Species interaction that benefits one and has little or no effect on the other  Example: Small plants growing in shade of larger plants  Epiphytes  Forehead mites

Bromeliad Commensalism Fig. 6-8, p. 118

Ecological Succession: Communities in Transition  What is ecological succession? (Gradual change in species composition)  Primary succession = establishment of communities on nearly lifeless ground (no soil) ex. glacier retreat, landslide, lava, abandoned parking lot  Secondary succession - community disturbed, soil remains. Burned / cut forests, polluted stream, flood

Two types of ecological succession animation. Animation

How Predictable is Succession?  Climax community concept - orderly sequence-  “Balance of nature”- old school  New views of equilibrium in nature -  Unpredictable succession - “The modern view is that we cannot project the course of a given 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 (capacity for growth)  Intrinsic rate of increase (r) (assumes unlimited resources)  No indefinite population growth  Environmental resistance = all the factors that limit population growth  Carrying capacity (K) - determined by biotic potential & enviro resistance

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

Exponential and Logistic Population Growth  Resources control population growth  Exponential growth - J-shaped curve  Logistic growth - S-shaped curve

Fig. 6-12, p. 121 Logistic Growth of Sheep Population Overshoot Carrying Capacity Year Number of sheep (millions)

When Population Size Exceeds Carrying Capacity  Switch to new resources, move or die  Overshoots  Reproductive time lag  Population dieback or crash  Human Famines - Irish potato famine million dead  Factors controlling human carrying capacity- technology has increased carrying capacity for humans

Exponential Growth, Overshoot and Population Crash of Reindeer Fig. 6-13, p. 122 Population Overshoots Carrying Capacity Population crashes Carrying capacity Year Number of sheep (millions) 2,000 1,500 1,

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

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

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

Fig. 6-17, p. 125 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 Human Impacts on Ecosystems Natural Capital Degradation Altering Nature to Meet Our Needs

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

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 Solutions: Implications of the Principles of Sustainability Solutions Principles of Sustainability How Nature WorksLessons 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

Animation Resources depletion and degradation interaction

Animation Area and distance effects interaction.