Chapter 53 Community Ecology

I. Interspecific Interactions Competition Competitive exclusion principle Niche – fundamental vs. realized Resource partitioning Character displacement Predation Adaptations Cryptic coloration Aposemetic coloration Mimicry

Table 53-1

LE 53-2 High tide High tide Chthamalus Chthamalus realized niche Balanus Chthamalus fundamental niche Balanus realized niche Ocean Ocean Low tide Low tide

A. insolitus usually perches on shady branches. A. ricordii LE 53-3 A. insolitus usually perches on shady branches. A. ricordii A. distichus perches on fence posts and other sunny surfaces. A. insolitus A. aliniger A. christophei A. distichus A. cybotes A. etheridgei

Santa María, San Cristóbal LE 53-4 G. fortis G. fuliginosa Beak depth Santa María, San Cristóbal 40 Sympatric populations 20 Los Hermanos Percentage of individuals in each size class 40 G. fuliginosa, allopatric 20 Daphne 40 G. fortis, allopatric 20 8 10 12 14 16 Beak depth (mm)

Figure 53-05

Figure 53-06

LE 53-7 Green parrot snake Hawkmoth larva

LE 53-8 Cuckoo bee Yellow jacket

Herbivory Parasitism Disease - pathogens Mutualism Commensalism Endoparasites, ectoparasites and parasitoidism Disease - pathogens Mutualism Commensalism

II. Dominant and Keystone Species and Control of Community Species diversity Species richness Relative abundance Trophic structure Food webs (Fig. 53.13) Limits on length Energetic hypothesis Dynamic stability hypothesis

LE 53-11 A B C D Community 1 A: 25% B: 25% C: 25% D: 25% Community 2 A: 80% B: 5% C: 5% D: 10%

A terrestrial food chain LE 53-12 Quaternary consumers Carnivore Carnivore Tertiary consumers Carnivore Carnivore Secondary consumers Carnivore Carnivore Primary consumers Herbivore Zooplankton Primary producers Plant Phytoplankton A terrestrial food chain A marine food chain

LE 53-13 Humans Smaller toothed whales Baleen whales Sperm whales Crab-eater seals Leopard seals Elephant seals Birds Fishes Squids Carnivorous plankton Euphausids (krill) Copepods Phyto- plankton

Sea nettle Juvenile striped bass Fish larvae Fish eggs Zooplankton

Number of trophic links LE 53-15 6 6 No. of species 5 5 No. of trophic links 4 4 Number of species Number of trophic links 3 3 2 2 1 1 High (control) Medium Low Productivity

Species with a Large Impact Dominant species Keystone species (Fig. 53.16, p. 1168) Foundation species Bottom-Up and Top-Down Controls Bottom-Up: NVHP Nutrients are limiting factors Top-Down: NVHP Predation is limiting factor

LE 53-16 With Pisaster (control) 20 15 Number of species present Without Pisaster (experimental) 10 5 1963 ’64 ’65 ’66 ’67 ’68 ’69 ’70 ’71 ’72 ’73

LE 53-17 100 80 Otter number (% max. count) 60 40 20 Sea otter abundance 400 300 Grams per 0.25 m2 200 100 Sea urchin biomass 10 8 Number per 0.25 m2 6 4 2 1972 1985 1989 1993 1997 Year Total kelp density Food chain before killer whale involvement in chain Food chain after killer whales started preying on otters

Figure 53-18

With Juncus Without Juncus LE 53-19 8 6 Number of plant species 4 2 With Juncus Without Juncus Salt marsh with Juncus (foreground) Conditions

herbaceous plant cover LE 53-20 100 75 herbaceous plant cover Percentage of 50 25 100 200 300 400 Rainfall (mm)

Polluted State Restored State Fish Abundant Rare Zooplankton Rare LE 53-UN1171 Polluted State Restored State Fish Abundant Rare Zooplankton Rare Abundant Algae Abundant Rare

III. Disturbance Influences Communities Definition and causes Changes in community and removal of species Human roles Ecological succession Primary Secondary

LE 53-21 Before a controlled burn. A prairie that has not burned for several years has a high propor-tion of detritus (dead grass). During the burn. The detritus serves as fuel for fires. After the burn. Approximately one month after the controlled burn, virtually all of the biomass in this prairie is living.

LE 53-22 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. One year after fire. This photo of the same general area taken the following year indicates how rapidly the com-munity began to recover. A variety of herbaceous plants, different from those in the former forest, cover the ground.

LE 53-24 Pioneer stage, with fireweed dominant Dryas stage Spruce 60 50 40 Soil nitrogen (g/m2) 30 20 10 Pioneer Dryas Alder Spruce Successional stage Spruce stage Nitrogen fixation by Dryas and alder increases the soil nitrogen content.

IV. Biogeographic Factors on Community Equatorial-Polar gradients Area effects Species-area curve (p. 1176) Island equilibrium model Size and distance from mainland Immigration/extinction

LE 53-25 180 160 140 120 Tree species richness 100 80 60 40 20 100 300 100 300 500 700 900 1,100 Actual evapotranspiration (mm/yr) Trees 200 100 Vertebrate species richness (log scale) 50 10 500 1,000 1,500 2,000 Potential evapotranspiration (mm/yr) Vertebrates

Number of species (log scale) 1,000 100 Number of species (log scale) 10 1 1 10 100 103 104 105 106 107 108 109 1010 Area (acres)

LE 53-27 Immigration Immigration Extinction Immigration Extinction (small island) (near island) Extinction (large island) (far island) Extinction Immigration (far island) Rate of immigration or extinction Immigration (large island) Rate of immigration or extinction Extinction Rate of immigration or extinction (near island) (small island) Equilibrium number Small island Large island Far island Near island Number of species on island Number of species on island Number of species on island Immigration and extinction rates Effect of island size Effect of distance from mainland

0.1 1 10 100 1,000 Area of island (mi2) (log scale) 400 200 100 50 Number of plant species (log scale) 25 10 5 0.1 1 10 100 1,000 Area of island (mi2) (log scale)

V. Views of Community Structure Integrated hypothesis Individualistic hypothesis

LE 53-29 Population densities of individual species Environmental gradient (such as temperature or moisture) Integrated hypothesis Population densities of individual species Environmental gradient (such as temperature or moisture) Individualistic hypothesis Number of per hectare plants 600 400 200 Wet Moisture gradient Dry Trees in the Santa Catalina Mountains