anolis.html: _FPX_18
53_03ResourcePartition.jpg
Resource partitioning among Dominican Republic lizards.
Seven species of Anolis lizards live in close proximity, and all feed on insects and other small arthropods.
However, competition for food is reduced because each lizard species has a different perch, thus occupying a distinct niche.
aposematic.html: 53_06AposematicColor.jpg
Aposematic coloration: poison arrow frog.
batesian.html: 53_07BatesianMimicry.jpg
Batesian mimicry: A harmless species mimics a harmful model.
biomanipulation.html: _FPX_18
53_UN1171BiomanipDiagram.jpg
In lakes with three trophic levels, removing fish should improve water quality by increasing zooplankton and
thereby decreasing algal populations.
In lakes with four trophic levels, adding top predators should have the same effect.
burn.html: 53_21GraslandFireImpact.jpg
| Long-term effects of fire on a tallgrass prairie community in Kansas. | ||||
|---|---|---|---|---|
| Before a controlled burn. A prairie that has not burned for several years has a high proportion of detritus (dead grass). | During the burn. The detritus serves as fuel for fires. The trees in the photographs were growing along a stream and were not burned. | After the burn. Approximately one month after the controlled burn, virtually all of the biomass in this prairie is living. | ||
cattle_egret.html: 53_10Commensalism.jpg
The cattle_egret, a species widely distributed in Africa, Eurasia, and Australia, was not found in the Americas 200 years ago.
Some of these strong–flying birds managed to fly across the Atlantic Ocean and colonize northeastern South America in the late 1800s.
They gradually spread northward into North America, reaching Florida in the 1950s.
Today they breed as far west as the Pacific Coast and as far north as southern Canada.
climatic.html: _FPX_18
| Energy, water, and species richness. | |||
|---|---|---|---|
| (a) | Species richness of North American trees increases most predictably with actual evapotranspiration, which is determined by the amount of solar radiation, temperature, and water availability. | (b) | Vertebrate species richness in North America increases most predictably with potential evapotranspiration, a measure of energy availability but not water availability, and is highest in regions of high solar radiation and temperature. |
commensalism.html: 53_10Commensalism.jpg
A possible example of commensalism between cattle egrets and water buffalo.
The egrets eat insects off the buffalo
. It is not clear if the buffalo benefits at all; the relationship may even be parasitic.
community-composition.html: _FPX_18
53_29CommunityHypothesesC.jpg
Trees in the Santa Catalina Mountains.
The distribution of tree species at one elevation in the Santa Catalina Mountains of Arizona supports the individualistic
hypothesis.
Each tree species has an independent distribution along the gradient,
apparently conforming to its tolerance for moisture, and the species that
live together at any point along the gradient have similar
physical requirements. Because the vegetation changes continuously along the gradient,
it is impossible to delimit sharp boundaries for the communities.
community-individualistic.html: _FPX_18
53_29CommunityHypothesesB.jpg
Individualistic hypothesis.
Species are independently distributed along gradients and a community is simply the assemblage of species that occupy
the same area because of similar abiotic needs.
community-integrated.html: _FPX_18
53_29CommunityHypothesesA.jpg
Testing the integrated and individualistic hypotheses of communities.
Ecologist Robert Whittaker tested these two hypotheses by graphing the abundance of different plant species (y –axis)
along environmental gradients of abiotic factors such as temperature or moisture (x–axis).
Each colored curve represents the abundance of one species.
Integrated hypothesis.
Communities are discrete groupings of particular species that are closely interdependent and nearly always occur together.
community.html: 53_01SavannaCommunity.jpg
A savanna community in Chobe National Park, Botswana.
cryptic.html: 53_05CrypticColoration.jpg
_MID_SeaHorses-V.swf 0 SeaHorses
Cryptic coloration: canyon tree frog.
deceptive.html: 53_x1DeceptiveColoration.jpg
Deceptive coloration.
A variation on deceptive coloration is startle
coloration.
disturbance.html: 53_2218x1aMtStHelens.jpg
diversity.html: 53_11MeasureDiversity.jpg
Which forest is more diverse?
Ecologists would say that community 1 has greater species diversity,
a measure that includes both species richness (the total number of different species in the community)
and relative abundance (the proportion each species represents of the total individuals in the community).
dominant.html: SugarMapleForest.jpg
ectoparasitism.html: MistletoeInSilverBirch.jpg
Mistletoe is a photosynthetic ectoparasite
of plants.
Endoparasitism
.
endoparasitism.html: ../ch33/33_11BloodFlukeLifCycl.jpg
The blood fluke is a human endoparasite.
parasitoidism
.
fangs.html: 53_SnakeFangs.jpg
| Patchiness and recovery following a large-scale disturbance. | ||
|---|---|---|
| Soon after fire. The 1988 Yellowstone National Park fire destroyed large areas of forests dominated by lodgepole pines. The burn left a patchy landscape. Note the unburned trees in the distance. | One year after fire. In the same general area the following year, the community began to recover rapidly. A variety of herbaceous plants, different from those in the former forest, cover the ground. | |
fire.html: 53_22x2ForestFire.jpg
food_chain.html: 53_12FoodChains.jpg
Examples of terrestrial and marine food chains.
The arrows trace energy and nutrients that pass through the trophic levels of a community when organisms feed on one another.
Decomposers, which “feed” on organisms from all trophic levels, are not shown here.
food_web-links.html: 53_15EnergyLimitFoodChain.jpg
Test of the energetic hypothesis for the restriction of food chain length.
Researchers manipulated the productivity of tree–hole communities in Queensland, Australia,
by providing leaf litter input at three levels:
high litter input = natural (control) rate of litter fall; medium = 1 / 10 natural rate; and low = 1 / 100 natural rate.
Reducing energy input reduced food chain length, a result consistent with the energetic hypothesis.
food_web-partial.html: 53_14EstuaryFoodWeb.jpg
Partial food web for the Chesapeake Bay estuary on the U.S. Atlantic coast.
The sea nettle (Chrysaora quinquecirrha ) and juvenile striped bass (Morone saxatilis) are the main predators of fish larvae
(bay anchovy and several other species). Note that sea nettles are secondary consumers (black arrows)
when they eat zooplankton and tertiary consumers (red arrows) when they eat fish larvae,
which are themselves secondary consumers of zooplankton.
food_web.html: 53_13AntarcticFoodWeb.jpg
An antarctic marine food web.
Arrows follow the transfer of food from the producers (phytoplankton) up through the trophic levels.
For simplicity, this diagram omits decomposers.
foundation-facilitator.html: 53_19Facilitation.jpg
Facilitation by black rush (Juncus gerardi) in New England salt marshes.
Black rush facilitates the occupation of the middle upper zone of the marsh by
shading the soil to prevent salt buildup.
Its presence increases local plant species richness.
foundation.html: 53_18BeaverEngineer.jpg
Beavers as ecosystem “engineers” in temperate and boreal forests.
By felling trees, building dams, and creating ponds,
beavers can transform large areas of forest into flooded wetlands.
geospiza.html: 53_04CharacterDisplace.jpg
Character displacement: indirect evidence of past competition.
When populations of Geospiza fuliginosa and Geospiza fortis are sympatric on Santa María and San Cristóbal, G. fuliginosa has a shallower, smaller beak and G. fortis a deeper, larger one (top graph), adaptations that favor eating different sizes of seeds.
Allopatric
populations
of these 2 species on other islands have similar beak morphologies (bottom two graphs) and can eat similarly sized seeds.
island.html: 53_27EquilibIslandBiogeog.jpg
| The equilibrium model of island biogeography. | ||||
|---|---|---|---|---|
| The equilibrium number of species on an island is a balance between the immigration of new species and the extinction of extant species. | Immigration rates tend to be higher and extinction rates lower on large islands, resulting in more species. | Immigration rates are also higher and extinction rates lower on near islands. | ||
keystone-sea_otter.html: 53_17OtterKeystonPredator.jpg
Sea otters as keystone predators in the North Pacific.
Sea otters (Enhydra lutris) feed on sea urchins,
which feed mainly on kelp.
In areas where sea otters are abundant, sea urchins are rare and kelp forests are well developed.
Over the last 20 years, killer whales have been preying on sea otters in Alaska as the whales' usual prey has declined.
The decline of sea otters as a keystone species has allowed sea urchin populations to increase,
resulting in the destruction of kelp forests.
keystone.html: 53_16KeystonePredator.jpg
Testing a keystone predator hypothesis.
Another example of keystone species is the sea otter
in kelp forest communities.
moisture.html: _FPX_18
53_20LimitFactorMoisture.jpg
Relationship between rainfall and herbaceous plant cover in a desert shrub community in Chile.
Moisture limitation on plant growth during dry non–El Niño years (red points)
creates strong bottom–up control on this community,
whereas abundant moisture during El Niño years (blue points) stimulates increased plant and animal abundance,
inducing strong top–down control.
mullerian.html: 53_08MullerianMimicry.jpg
Müllerian mimicry: Two unpalatable species mimic each other.
mutualism.html: 53_09Mutualism.jpg
Mutualism.
Some acacia trees have hollow thorns that house stinging ants which
feed on sugar secreted by nectaries and on protein–rich swellings.
The acacia benefits because the ants attack anything that touches the tree.
Ants can also be mutualistic with
fungi
and
caterpillars.
Other examples include mycorrhizae
, cleaner
shrimp
and
gobies
,
and Clownfish/Anemone
relationships.
parasitism.html: MistletoeInSilverBirch.jpg
parasitoidism.html: Hornworm_parasites.jpg
Parasitoidism
.
A female wasp lays eggs in a living Tomato Hornworm caterpillar;
the larvae hatch and feed on the body of the host, eventually killing it.
predator.html: _FPX_18
Lynx-hare.jpg
Video:
Whale Eating a Seal
species-area.html: 53_26SpeciesAreaCurve.jpg
Species-area curve for North American breeding birds (logarithmic scale_.
The data points range from a 0.5–acre plot with 3 species in Pennsylvania to the whole United States and Canada
(4.6 billion acres) with 625 species.
species-area_study.html: 53_28SpeciesAreaTheory.jpg
Ecologists Robert MacArthur and E. O. Wilson found that on the Galápagos Islands,
plant species richness increased with island size, supporting the species-area theory.
succession-primary.html: 53_23GlacialRetreat.jpg
A glacial retreat in southeastern Alaska.
The dated locations chronicle recession of the glacier since 1760, based on historical description.
As the ice retreats, it leaves moraines along the edge of the bay, on which primary succession occurs.
succession-secondary.html: 53_24CommunitSuccession.jpg
Succession at Glacier Bay, Alaska.
Plant species composition changes dramatically during succession at Glacier Bay, accompanied by changes in abiotic factors.
Pioneering species such as liverworts, mosses, and fireweed build up the soil.
Nitrogen fixation by Dryas and Alder enrich the soil, leading to a spruce–hemlock climax forest.