A. Lizard species perches on fences and other sunny surfaces. B. lizard species usually perches on shady branches. Resource partitioning is differentiation of ecological niches, enabling similar species to coexist in a community A. ricordii Figure 54.2 Resource partitioning among Dominican Republic lizards A. insolitus A. aliniger A. christophei A. distichus A. cybotes A. etheridgei

How a species’ niche can be influenced by interspecific competition? Later - Realized Niche High tide Chthamalus Chthamalus realized niche Balanus Balanus realized niche Ocean Low tide Ist - Fundamental Niche High tide Figure 54.3 Can a species’ niche be influenced by interspecific competition? Chthamalus fundamental niche Ocean Low tide

Character displacement: Indirect Evidence of Past Competition G. fuliginosa G. fortis Beak depth 60 Los Hermanos 40 G. fuliginosa, allopatric 20 60 Daphne Percentages of individuals in each size class 40 G. fortis, allopatric 20 Figure 54.4 Character displacement: indirect evidence of past competition 60 Santa María, San Cristóbal Sympatric populations 40 20 8 10 12 14 16 Beak depth (mm)

Müllerian mimicry: Two “yuck” Cryptic coloration Canyon tree frog (b) Aposematic coloration Poison dart frog (c) Batesian mimicry: A harmless species mimics a harmful one. Hawkmoth larva Figure 54.5 Examples of defensive coloration in animals (d) Müllerian mimicry: Two “yuck” unpalatable species mimic each other. Cuckoo bee Green parrot snake Yellow jacket

A possible example of commensalism between cattle egrets (birds) and water buffalo: The Birds eat insects disturbed by the Buffalo as they move. Figure 54.8 A possible example of commensalism between cattle egrets and water buffalo

Terrestrial and Marine Food Chains Quaternary consumers Carnivore Carnivore Tertiary consumers Carnivore Carnivore Secondary consumers Carnivore Carnivore Figure 54.11 Examples of terrestrial and marine food chains Primary consumers Herbivore Zooplankton Primary producers Plant Phytoplankton A terrestrial food chain A marine food chain

An Antarctic Marine Food Web Humans Smaller toothed whales Baleen whales Sperm whales Crab-eater seals Leopard seals Elephant seals Birds Fishes Squids Figure 54.12 An antarctic marine food web Carnivorous plankton Euphausids (krill) Copepods Phyto- plankton

Seastar are keystone predators Seastar are keystone predators. They are key in preserving species diversity in their ecosystem. EXPERIMENT RESULTS Figure 54.15 Is Pisaster ochraceus a keystone predator? 20 15 With Pisaster (control) Number of species present 10 5 Without Pisaster (experimental) 1963 ’64 ’65 ’66 ’67 ’68 ’69 ’70 ’71 ’72 ’73 Year

Sea otters are keystone predators in the North Pacific 100 80 Otter number (% max. count) 60 40 20 (a) Sea otter abundance 400 300 Grams per 0.25 m2 200 100 (b) Sea urchin biomass Figure 54.16 Sea otters as keystone predators in the North Pacific 10 8 Number per 0.25 m2 6 4 2 1972 1985 1989 1993 1997 Year (c) Total kelp density Food chain

Beavers are a Foundation Species = ecosystem“engineers” Figure 54.17 Beavers as ecosystem “engineers”

The large-scale fire in Yellowstone National Park in 1988 demonstrated that communities can often respond very rapidly to a massive disturbance. Figure 54.21 Recovery following a large-scale disturbance (a) Soon after fire (b) One year after fire

Pioneer stage = soil builders / fireweed dominant Figure 54.22 Glacial retreat and primary succession at Glacier Bay, Alaska 1 Pioneer stage = soil builders / fireweed dominant

Dryas stage grasses and shrubs Figure 54.22 Glacial retreat and primary succession at Glacier Bay, Alaska 2 Dryas stage grasses and shrubs

Alder stage: trees and shrub Figure 54.22 Glacial retreat and primary succession at Glacier Bay, Alaska 3 Alder stage: trees and shrub

Spruce stage = Climax Community STABLE Figure 54.22 Glacial retreat and primary succession at Glacier Bay, Alaska 4 Spruce stage = Climax Community STABLE

Changes in soil nitrogen content during succession at Glacier Bay 60 50 40 Soil nitrogen (g/m2) 30 20 Figure 54.23 10 Pioneer Dryas Alder Spruce Successional stage

Disturbance of the ocean floor by trawling Figure 54.24 Disturbance of the ocean floor by trawling

The equilibrium model of island biogeography Immigration Extinction Immigration Extinction Immigration (small island) (near island) Extinction (large island) (far island) Extinction Immigration Rate of immigration or extinction Rate of immigration or extinction (large island) Rate of immigration or extinction (far island) Extinction Immigration (near island) (small island) Equilibrium number Small island Large island Far island Near island Number of species on island Figure 54.27 The equilibrium model of island biogeography Number of species on island Number of species on island (a) Immigration and extinction rates (b) Effect of island size (c) Effect of distance from mainland

White-band disease on coral is destroying the reef. Figure 54.29

Review

You should now be able to: Distinguish between the following sets of terms: competition, predation, herbivory, symbiosis; fundamental and realized niche; cryptic and aposematic coloration; Batesian mimicry and Müllerian mimicry; parasitism, mutualism, and commensalism; endoparasites and ectoparasites; species richness and relative abundance; food chain and food web; primary and secondary succession.

Define an ecological niche and explain the competitive exclusion principle in terms of the niche concept. Explain how dominant and keystone species exert strong control on community structure. Distinguish between bottom-up and top-down community organization. Describe and explain the intermediate disturbance hypothesis.

Explain why species richness declines along an equatorial-polar gradient. Define zoonotic pathogens and explain, with an example, how they may be controlled.