Community Ecology
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Community Ecology Community Ecology Presentation Transcript

  • COMMUNITY ECOLOGY: STRUCTURE, SPECIES INTERACTIONS, SUCCESSION, AND SUSTAINABILITY The Walker School Environmental Science
  • 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?
  • 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
  • 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
  • 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
  • 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.
  • WHAT IS A COMMUNITY?
  • Typical Community What abiotic and biotic components are involved in this community?
  • Community Variables Physical Appearance  Types of Species  Number of Species  Ecological Niches 
  • 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
  • Types of Species Species Richness (number of different species)  Species Evenness (population size)  Niche Structure (number of niches) 
  • Niches Fundamental  Niche  Determined by abiotic factors Realized Niche   Determined by species competition
  • WHERE IS MOST OF THE WORLD’S BIODIVERSITY FOUND?
  • Rich Environments Have Low Species Evenness Tropical Rain Forests  Coral Reefs  The Deep Sea  Large Tropical Lakes 
  • Richness Variables Latitude  Pollution  Habitat Diversity  Net Primary Productivity (NPP)  Habitat Disturbance  Time 
  • 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”?
  • WHAT DIFFERENT ROLES DO VARIOUS SPECIES PLAY IN ECOSYSTEMS?
  • Species Classification Native (indigenous)  Nonnative (invasive)  Indicator  Keystone  Foundation  Pioneer 
  • Animals Native to Georgia http://georgiawildlife.dnr.state.ga.us/
  • WHAT ARE INVASIVE SPECIES?
  • US Invasive Species http://www.invasive.org/
  • U.S. Invasive Species African Bees Ragweed   Cane Toads Japanese Maple   Zebra Mussels Kudzu   Sea Lamprey  European Starling  Bull Frog  Flat Head Catfish 
  • Invasive Species in Georgia http://www.gainvasives.org/
  • WHAT DETERMINES THE NUMBER OF SPECIES ON ISLANDS?
  • 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 
  • © 2004 Brooks/Cole – Thomson Learning Number of amphibian and reptile species SABA MONTSERRAT CUBA Hispaniola 100 Cuba Puerto Rico Jamaica 10 Montserrat Saba Redonda 1 10 100 1,000 10,000 100,000 Area (square miles)
  • HOW ARE NATIONAL PARKS LIKE ISLANDS?
  • Map of US National Parks http://www.nps.gov How are national parks like islands; how are they different?
  • Yellowstone National Park Example What role does geology play in biological isolation?
  • 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.
  • National Parks by Area
  • 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.
  • WHAT ARE INDICATOR SPECIES?
  • 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
  • WHY ARE AMPHIBIANS VANISHING?
  • 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.
  • Warnings from Frogs Habitat Loss and Fragmentation  Pollution  Increases in UV Radiation  Over Hunting  Parasitism  Disease  Non-native Predators 
  • Ecological Role of Frogs Indicators that environmental quality is deteriorating  They consume more insects than birds  Represent a storehouse of pharmaceutical products 
  • Pharmaceutical Uses Painkillers  Antibiotics 
  • WHAT ARE KEYSTONE SPECIES?
  • 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. 
  • Example of Keystone Species Bees Lion   Humming Birds Alligator Frogs   Bats Dung Beetle   Great White Sharks Sea Stars   Leopard  Sea Otters 
  • Activity: Movie Watch the National  Geographic movie “The Wolves of Yellowstone” Write an essay  explaining the role of wolves in the northern coniferous forests.
  • WHAT ARE FOUNDATION SPECIES?
  • 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.
  • HOW DO SPECIES INTERACT?
  • Types of Interactions Between members of the same species  (intraspecific) Between different species (interspecific) 
  • High Paramecium Relative population density aurelia Paramecium caudatum Low 0 2 4 6 8 10 12 14 16 18 Days Both species grown together
  • Interspecific Competition Predation ( + - )  Parasitism ( - - )  Mutualism ( + + )  Commensalism ( + 0 ) 
  • Resource Partitioning of Warblers in Spruce Trees
  • Character Displacement
  • HOW HAVE SOME SPECIES REDUCED OR AVOIDED COMPETITION?
  • Organisms share resources to not compete.
  • Organisms specialize in a niche not to compete.
  • HOW DO PREDATOR AND PREY SPECIES INTERACT?
  • 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)
  • Types of Predation Herbivores (grass)  Fructivores (fruits)  Insectivores (insects)  Carnivores (meat) 
  • Modes of Predation Pursuit  Ambush  Pursuit Types •Run •Swim •Fly •Dive
  • Avoidance Smell  Shells  Spines  Thorns  Camouflage (cryptic coloration)  Alarm Calls  Size Limitation (too big to eat) 
  • Batesian Mimicry A palatable or  harmless species mimics an unpalatable or harmful species
  • Chemical Warfare Poisonous  Irritating  Foul Smelling  Bad Tasting 
  • Common Herbivore Poisons Cocaine  Caffeine  Cyanide  Opium  Strychnine  Peyote  Nicotine  Rotenone 
  • Common Herbivore Repellants Pepper  Mustard  Nutmeg  Oregano  Cinnamon  Mint 
  • Deceptive Looks & Behavior Puffing Up  Spreading Wings  Spreading Hoods  Mimicking a Predator 
  • WHAT ARE PARASITES, AND WHY ARE THEY IMPORTANT?
  • Parasitism Ectoparasitism (external parasites)  Endoparasitism (internal parasites)  Parasitoidism (laying eggs in host)  Role of Parasites •Glue Communities Together •Promote Biodiversity
  • Common Ectoparasites Ticks  Fleas  Mosquitoes  Mistletoe Plants  Athlete’s Foot  American Dog Tick Laying Eggs
  • Dog and Cat Flea
  • Mosquitoes
  • Mistletoe Plants
  • Athlete’s Foot
  • Common Endoparasitic Organisms Bacteria  Viruses  Protists  Fungi  Prions  Worms 
  • Worm Parasites Tapeworm  Hookworm  Pinworm  Roundworm  Schistosoma  Tapeworm
  • Hookworm
  • Ringworm
  • Common Water Parasites Giardia lamblia  Cryptosporidium parvum 
  • HOW DO SPECIES INTERACT SO THAT BOTH SPECIES BENEFIT?
  • Types of Mutualism Pollination Mutualism  Nutritional Mutualism  Inhabitant Mutualism 
  • 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
  • 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.
  • HOW DO SPECIES INTERACT SO THAT ONE BENEFITS BUT THE OTHER IS NOT HARMED?
  • Commensalistic Organisms Redwood Sorrel  Orchids  Bromeliads 
  • HOW DO ECOSYSTEMS RESPOND TO CHANGE?
  • Types of Succession Primary  Secondary  Types of Primary Succession •Glaciers •Volcanic Eruptions •Asteroid Impacts •Mountain Top Removal Fireweed and glacial moraine in Alaska Types of Secondary Succession •Fires •Hurricanes •Earthquakes
  • Pioneer Species Lichens  Mosses  Weeds  Grasses 
  • 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 
  • 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
  • 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 
  • 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 
  • HOW DO SPECIES REPLACE ONE ANOTHER IN ECOLOGICAL SUCCESSION?
  • Succession of Organisms © 2004 Brooks/Cole – Thomson Learning Early Successional Midsuccessional Late Successional Wilderness Species Species Species Species Rabbit Elk Turkey Grizzly bear Quail Moose Martin Wolf Hammond’s Ringneck pheasant Deer Caribou Dove Ruffled grouse flycatcher Bighorn sheep Bobolink Snowshoe hare Gray squirrel California condor Pocket gopher Bluebird Great horned owl Ecological succession
  • Rate of Succession Variables Facilitation  Inhibition  Tolerance 
  • HOW DO DISTURBANCES AFFECT SUCCESSION AND SPECIES DIVERSITY?
  • 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
  • Intermediate Disturbance Hypothesis Dynamic Equilibrium  Promotes Heterogeneity  Promotes Evolution  Fallen trees, costal redwoods
  • Species diversity How Disturbances Affect Species Biodiversity 0 100 Percentage disturbance
  • Things are Always Changing Succession is not a linear progression  No Climax Communities  No True Homeostasis  Dynamic Equilibrium 
  • Aspects of Stability Persistence  Constancy  Resilience 
  • 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 
  • WHY SHOULD WE BROTHER TO PROTECT NATURAL SYSTEMS?
  • Precautionary Principle Monitor cause and effect relationships  Complete risk analysis studies before beginning  Take acceptable risks to learn  Complete independent reviews of our actions 
  • Research Helps Us to Evaluate Environmental Issues Agricultural Landscapes  National Parks  Reservoirs  Marine Fisheries 
  • 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
  • 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