Community Ecology

Chapter 7

The flying fox

Keystone species in tropical rainforest Pollinates plants while drinking nectar Spreads seed of fruit eaten Mutualistic relationship with durian fruit Help regenerate open areas through

seed dispersal (80-90% new seed) Decline in numbers from deforestation

and hunting

Dispersal of diversity

Groups are arranged either in clumps (most common), uniformly, or randomly

Edge effects are ecotones where different species may live. Usually different microclimate than adjoining areas

Largest Biodiversity

Tropical rainforest Coral reefs Deep sea Tropical lakes Also considered species rich

Tropical dry habitats Temperate shrublands (chaparral)

Biodiversity continued

Most diversity near equator Higher availability of resources Less evolutionary time High diversity leads to higher diversity More pressure from disease and parasites Speciation higher than background

extinction

Diversity in marine systems

Higher diversity near 2000 meters and on bottom More stable away from surface Lack of nutrients below 2000m Abundant nutrient on bottom and variation

of habitats

Pollution lowers diversity (never would have guessed that)

Diversity on Islands

The bigger the more diverse

The farther from mainland the less diverse

Nonnative species

Also called alien, exotic and introduced Generally have no natural predators so

population goes unchecked, seriously damaging the ecosystem

Often introduced by accident Cargo from foreign areas Pets and house plants that “escape” “Natural” migration due to climate changes

Prime players

Indicator species – serves as an early warning that an ecosystem is declining Birds – low birth rates, thin shells, birth defects

Keystone species – a species that contributes greatly to an ecosystem even though they may not dominate in numbers Seed dispersal/pollination (birds) Habitat modification (beaver) Efficient recycling of matter

Species interaction

Intraspecific competition – competing with your own species

Interspecific competition – competing with another species

Compete over food, shelter, space, breeding, etc.

Dibs, I saw it first!

Interference competition – when two or more species try to limit access to a resource (some humming birds defend particular trees)

Exploitation competition – when one group uses a resource faster than another (can lead to competitive exclusion principle (one dies out))

How to avoid competition

Resource partitioning – using a limited resource at different times, in different places or different ways

Think about how similar all birds are, but through evolution have developed different feeding patterns (beaks)

Fig. 8.9, p. 182

Black skimmerseizes small fishat water surface

Flamingofeeds on minuteorganismsin mud

Scaup and otherdiving ducks feed onmollusks, crustaceans,and aquatic vegetation

Louisiana heron wades intowater to seize small fish

Brown pelican dives for fish,which it locates from the air

Avocet sweeps bill throughmud and surface water in search of small crustaceans,insects, and seeds

Oystercatcher feeds onclams, mussels, and other shellfish into which it pries its narrow beak

Dowitcher probes deeplyinto mud in search ofsnails, marine worms,and small crustaceans

Herring gull is atireless scarialavenger

Ruddy turnstone searchesunder shells and pebblesfor small invertebrates

Knot (a sandpiper)picks up worms andsmall crustaceans leftby receding tide

Piping plover feedson insects and tinycrustaceans on sandy beaches

Predator-Prey relationship

Needed to keep gene pool strong Slow, sick, less agile, etc. “weak” are

more easily caught, and are therefore removed from the gene pool. This strengthens the remaining population

Symbiotic interactions

3 types of symbiosis – parasitism, mutualism, and commensalism

Parasitism – one species (parasite) feeds on another organism (host) by living in or on the host.

Parasites help promote biodiversity by controlling population size (eliminates the weak)

Mutualism

Two organisms (different species) interact and both benefit from the relationship

Examples Clownfish/Anemones Tickbird/Rhinoceros Protozoan/Termites

Fig. 8.13, p. 187

Commensalism

Two species interact, one benefits and the other is unaffected.

Some trees have mosses or epiphytes growing on them

Fig. 8.14, p. 187

Succession

Primary succession – takes place on new rock or lifeless ground

Mosses/lichen begin to turn rock to soil Small fast growing plants take root (weeds) Larger plants grow in the nutrient enhanced

soil Trees immigrate in from birds Mature ecosystem (forest) climax community

Secondary succession

Same as primary except in an area that once had life, but was ruined during a catastrophe (fire, flood, farming, etc.)

Fig. 8.17, p. 190

Early SuccessionalSpecies

RabbitQuailRingneck pheasantDoveBobolinkPocket gopher

MidsuccessionalSpecies

ElkMooseDeerRuffled grouseSnowshoe hareBluebird

Late SuccessionalSpecies

TurkeyMartinHammond’sFlycatcherGray squirrel

WildernessSpecies

Grizzly bearWolfCaribouBighorn sheepCalifornia condorGreat horned owl

Ecological succession

Sustainability

What maintains an ecosystem Inertia or persistence – ability of a

system to resist disturbances Constancy – keep population level

stable Resilience – ability to bounce back from

a disturbance

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