Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint TextEdit Art Slides for Biology, Seventh Edition Neil Campbell and Jane Reece Chapter 53 Community Ecology

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 53.1 A savanna community in Chobe National Park, Botswana

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings What is a niche? An area is thus defined, each point of which corresponds to a possible environmental state… an n-dimensional hypervolume is defined, every point in which corresponds to a state of the environment which would permit the species.. to exist indefinitely. ~ G. Evelyn Hutchinson, “Father or modern ecology” In other words, the organism’s role in the ecosystem.

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings When Connell removed Balanus from the lower strata, the Chthamalus population spread into that area. The spread of Chtamalus when Balanus was removed indicates that competitive exclusion makes the realized niche of Chthamalus much smaller than its fundamental niche. RESULTS CONCLUSION Ocean Ecologist Joseph Connell studied two baranacle species  Balanus balanoides and Chthamalus stellatus  that have a stratified distribution on rocks along the coast of Scotland. EXPERIMENT In nature, Balanus fails to survive high on the rocks because it is unable to resist desiccation (drying out) during low tides. Its realized niche is therefore similar to its fundamental niche. In contrast, Chthamalus is usually concentrated on the upper strata of rocks. To determine the fundamental of niche of Chthamalus, Connell removed Balanus form the lower strata. Low tide High tide Chthamalus fundamental niche Chthamalus realized niche Low tide High tide Chthamalus Balanus realized niche Balanus Ocean Competitive Exclusion Principle

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Classic experiments confirm this. Fig. 53.2

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 53.3 Resource partitioning among Dominican Republic lizards A. insolitus usually perches on shady branches. A. distichus perches on fence posts and other sunny surfaces. A. distichus A. ricordii A. insolitus A. christophei A. cybotes A. etheridgei A. alinigar

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Character displacement is the tendency for characteristics to be more divergent in sympatric populations of two species than in allopatric populations of the same two species. – Hereditary changes evolve that bring about resource partitioning. Fig. 53.4

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 53.5 Cryptic coloration: canyon tree frog

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Holding the line of its near vertical posture, a yellow trumpetfish swims gracefully in the waters of the Tuamotu archipelago in French Polynesia. Trumpetfish tend to align themselves with other vertical objects, often hiding alongside larger upright-oriented fish to get closer to prey

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Mechanical defenses include spines. Chemical defenses include odors and toxins Aposematic coloration is indicated by warning colors, and is sometimes associated with other defenses (toxins). Fig Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 53.7 Batesian mimicry: A harmless species mimics a harmful one (a) Hawkmoth larva (b) Green parrot snake

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Figure 53.8 Müllerian mimicry: Two unpalatable species mimic each other (a) Cuckoo bee (b) Yellow jacket

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Possible interspecific interactions are introduced are symbolized by the positive or negative affect of the interaction on the individual populations. 1. Populations may be linked by competition, predation, mutualism and commensalism Symbiosis

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Interspecific Interactions

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings – Parasites and pathogens as predators. A parasite derives nourishment from a host, which is harmed in the process. Pathogens are disease-causing organisms that can be considered predators.

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Endoparasites live inside the host

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings ectoparasites live on the surface of the host.

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Parasitoidism is a special type of parasitism where the parasite eventually kills the host.

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 53.9 Mutualism between acacia trees and ants

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Mutualism is where two species benefit from their interaction. Fig Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

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Figure A possible example of commensalism between cattle egrets and water buffalo

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Commensalism is where one species benefits from the interaction, but other is not affected. An example would be barnacles that attach to a whale.

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Coevolution and interspecific interactions. – Coevolution refers to reciprocal evolutionary adaptations of two interacting species. When one species evolves, it exerts selective pressure on the other to evolve to continue the interaction. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Flower is white and blooms at night

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Flower is red and nectar is at the end of a long tube

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure Which forest is more diverse? Community 1 A: 25%B: 25%C: 25%D: 25% Community 2 A: 80%B: 5%C: 5%D: 10% D C B A

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 2. Species richness generally declines along an equatorial-polar gradient Tropical habitats support much larger numbers of species of organisms than do temperate and polar regions. In aquatic systems, biodiversity increases with depth. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The trophic structure of a community is determined by the feeding relationships between organisms. The transfer of food energy from its source in photosynthetic organisms through herbivores and carnivores is called the food chain. 2. Trophic structure is a key factor in community dynamics Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Charles Elton first pointed out that the length of a food chain is usually four or five links, called trophic levels. He also recognized that food chains are not isolated units but are hooked together into food webs. Fig

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Food webs. – Who eats whom in a community? – Trophic relationships can be diagrammed in a community. – What transforms food chains into food webs? – A given species may weave into the web at more than one trophic level. Fig Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure Partial food web for the Chesapeake Bay estuary on the U.S. Atlantic coast Sea nettle Fish larvae Zooplankton Fish eggs Juvenile striped bass

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings – What limits the length of a food chain? The energetic hypothesis suggests that the length of a food chain is limited by the inefficiency of energy transfer along the chain. The dynamic stability hypothesis states that long food chains are less stable than short chains. Fig Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure Test of the energetic hypothesis for the restriction of food chain length High (control) Medium Low Productivity No. of species No. of trophic links Number of species Number of trophic links

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure Testing a keystone predator hypothesis (a) The sea star Pisaster ochraceous feeds preferentially on mussels but will consume other invertebrates. With Pisaster (control) Without Pisaster (experimental) Number of species present ´64 ´65 ´66 ´67 ´68 ´69 ´70 ´71 ´72 ´73 (b) When Pisaster was removed from an intertidal zone, mussels eventually took over the rock face and eliminated most other invertebrates and algae. In a control area from which Pisaster was not removed, there was little change in species diversity.

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Keystone species exert an important regulating effect on other species in a community. Fig Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Food chain before killer whale involve- ment in chain (a) Sea otter abundance (b) Sea urchin biomass (c) Total kelp density Number per 0.25 m Grams per 0.25 m 2 Otter number (% max. count) Year Figure Sea otters as keystone predators in the North Pacific Food chain after killer whales started preying on otters

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure Beavers as ecosystem “engineers” in temperate and boreal forests

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure Facilitation by black rush (Juncus gerardi) in New England salt marshes Salt marsh with Juncus (foreground) With Juncus Without Juncus Number of plant species Conditions

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure Relationship between rainfall and herbaceous plant cover in a desert shrub community in Chile Rainfall (mm) Percentage of herbaceous plant cover

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings How would manipulation of any of these factors affect the others? Fish Zooplankton Algae Abundant Rare Abundant Rare Polluted State Restored State

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Primary Succession Primary succession is one of two types of biological and ecological succession of plant life. No existing “ecological infrastructure” New substrate devoid of vegetation and usually lacking soil, such as a lava flow or area left from retreated glacier. Pioneer species colonize first, break down rock into soil. Organisms like lichens, certain species of photosynthetic algae

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Secondary succession occurs where an existing community has been cleared by some event, but the soil is left intact. – Grasses grow first, then trees and other organisms. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Disturbances are events like fire, weather, or human activities that can alter communities. – Some are routine. 1. Most communities are in a state of non-equilibrium owing to disturbances Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure Long-term effects of fire on a tallgrass prairie community in Kansas (a) Before a controlled burn. A prairie that has not burned for several years has a high propor- tion of detritus (dead grass). (b)During the burn. The detritus serves as fuel for fires. (c) After the burn. Approximately one month after the controlled burn, virtually all of the biomass in this prairie is living.

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure Patchiness and recovery following a large-scale disturbance (a) Soon after fire. As this photo taken soon after the fire shows, the burn left a patchy landscape. Note the unburned trees in the distance. (b) One year after fire. This photo of the same general area taken the following year indicates how rapidly the community began to recover. A variety of herbaceous plants, different from those in the former forest, cover the ground.

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure Changes in plant community structure and soil nitrogen during succession at Glacier Bay, Alaska (b) Dryas stage (c) Spruce stage (d) Nitrogen fixation by Dryas and alder increases the soil nitrogen content. Soil nitrogen (g/m 2 ) Successional stage Pioneer Dryas Alder Spruce (a) Pioneer stage, with fireweed dominant

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Soil concentrations of nutrients show changes over time. Fig Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Intermediate Disturbance Hypothesis The Intermediate Disturbance Hypothesis (IDH) states that local species diversity is maximized when ecological disturbance is neither too rare nor too frequent. Evidence has both supported and failed to support the idea!

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure Energy, water, and species richness (a) Trees ,100 Actual evapotranspiration (mm/yr) (b) Vertebrates 500 1,000 1,500 2,000 Potential evapotranspiration (mm/yr) Vertebrate species richness (log scale) Tree species richness

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure Species-area curve for North American breeding birds Area (acres) Number of species (log scale) ,000

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure The equilibrium model of island biogeography Link to original paper Link to original paper Number of species on island (a) Immigration and extinction rates. The equilibrium number of species on an island represents a balance between the immigration of new species and the extinction of species already there. (b) Effect of island size. Large islands may ultimately have a larger equilibrium num- ber of species than small islands because immigration rates tend to be higher and extinction rates lower on large islands. Number of species on island (c) Effect of distance from mainland. Near islands tend to have larger equilibrium numbers of species than far islands because immigration rates to near islands are higher and extinction rates lower. Equilibrium number Rate of immigration or extinction Small island Large islandFar island Near island Immigration Extinction Immigration Extinction Immigration (small island) (large island) (small island) Immigration Extinction Immigration (far island) (near island) (far island) Extinction

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure How does species richness relate to area? The results of the study showed that plant species richness increased with island size, supporting the species-area theory. FIELD STUDY RESULTS Ecologists Robert MacArthur and E. O. Wilson studied the number of plant species on the Galápagos Islands, which vary greatly in size, in relation to the area of each island. CONCLUSION Area of island (mi 2 ) (log scale) Number of plant species (log scale) ,