species interactions & community ecology chapter 6

Species Interactions & Community Ecology

Chapter 6

MARSH HAWK

CROW

UPLAND SANDPIPER

GARTER SNAKE

FROG

SPIDER WEASEL BADGER COYOTE

GROUND SQUIRRELPOCKET GOPHER

PRAIRIE VOLE

CLAY-COLORED SPARROW

EARTHWORMS, INSECTS (E.G., GRASSHOPPPERS, CUTWORMS)

FIRST TROPHIC LEVEL Primary

producers

SECOND TROPHIC

LEVEL Primary consumers

(e.g., herbivores)

HIGHER TROPHIC LEVELS

Complex array of carnivores,

omnivores and other

consumers. Many feed at

more than one trophic level continually,

seasonally, or when an

opportunity presents itself

Typical Food Web

1. Maple seedling growing under an oak tree

2. Fungus (mycorrhizae) live on plant roots and facilitate water absorption

3. Frog eats a fly

4. Your dog has fleas

5. A bacteria grown in culture produces toxins that prevent others from growing near it

6. A hermit crab uses a discarded snail shell for protection

Competitive Exclusion Principle:

• When 2 species compete the more fit one will win. Two species cannot coexist in the same habitat with the same requirements for very long.

• Ex: gray squirrel vs red squirrel

It’s Squirrel versus Squirrel!

How can all these species coexist? NICHES!

• They can coexist if they utilize resources under different environmental conditions.

• Niche: the role a species plays in its habitat and under what environmental conditions.

• Fundamental Niche: conditions species can exist w/o competition.

• Realized Niche: conditions species can exist with competition. (Real world!)

Where do they belong?

• Endemic species– Native to a particular area and not elsewhere

• Exotic/non-native species– Introduced into a new geographic area

• Invasive species– Exotic that can run an endemic out of its habitat

• Cosmopolitan species– Broad distribution in suitable environments

• Ubiquitous species– They’re everywhere!

Pigeon Mouse

Lorius Lory of New GuineaRabbits of Australia

Japanese Maple in NJ

Feral Rabbits in Australia, 1963

Introduced in 1859. Diseases like myxomatosis(1991) and rabbit hemorrhagic disease (1996) were introduced in to control their numbers. Has lead to genetic resistance (esp myxomatosis)

Ecological Succession

Restoration

Previous Ideas on Restoration:• “Balance of Nature” Idea (until mid 20th century)• Equilibrium: nature left alone will achieve a

permanency of form & structure forever—the climax state.

• When there is a disturbance and then the force is removed, nature will return to its former, identical state.

• There’s a place for every creature and every creature in its place.

• Disturbance is bad…

But now…

• Nature is not constant.

• All ecosystems continually undergo change.

• Species evolve and adapt to change

• Many species require change to survive

To What Point Do We Restore?

• Pre-settlement of humans

• Restoration ecology

• Florida Everglades– Restoring wetlands– Improving water quality– Improving habitats of 60+ endangered

species

• Midwestern Prairies

How do we restore it?

• Depends on the situation.

• Redirecting water flow (adding/removing channels, dredging)

• Leave it alone/improve what goes into it

• Controlled burning

Succession:

• Natural recovery of a disturbed ecosystem. • Primary: initial establishment & development of

an ecosystem where one did not previously exist. Originally an abiotic environment. Ex: edges of lava flows, receding glaciers

• Secondary: reestablishment of an ecosystem following a disturbance. Some life will still remain. Ex: areas of fire or hurricane, abandoned farmland.

Primary Succession on a lava flow. Pioneer species had already taken hold

Secondary succession: boreal forest after a fire

Stages of Succession

• Early: plants with short life cycles, rapid seed dispersal. Stablize soil (aka 1st and 2nd stages). Often annual plants that can tolerate harsher conditions (much water, full sun, limited water, etc)– Biomass & Biodiversity both increase.

• Middle (3rd stage); larger plants, trees begin to dominate once early stage plants have made conditions more livable. Highest biodiversity

• Late (4th stage): Large, mature plants, larger animals. Slower growing, grow well in shade, have seeds that can persist.

Chemical cycling during succession:

• Organic material & other chemicals in soil increase throughout succession, but not indefinitely.

• If there is no disturbance, the ecosystem will use up stored chemicals and will no longer support late stage plants.

Biomes

• Regional complex of similar communities

• Dominant plant types & structure

http://www.globalchange.umich.edu

Precipitation, Latitude and Biomes

Temperate Deciduous Forest

Oaks, Beech, Maple; moderate temps & rain

Temperate Grasslands(steppe, prairie)

Tall grasses; less rainfall, more extreme temps between seasons

Temperate Rainforest

Hoh Rain Forest of Washington State;

Conifers such as cedars, spruce, hemlock, Douglas fir.

Heavy rainfall, moderate temps

Tropical Rain Forest

Warm temps year round; heavy rainfall; closer to equator.

Poor soils, high diversity of species

Tropical Deciduous Forest(Tropical Dry Forest)

Warm year-round w/moderate rainfall

Can have Monsoon seasons

Leaves may drop during dry seasons

Savanna

Warm year round; dry. Grasses

Deserts

Sparse rainfall

May have large daily temp fluctuations

Plants w/small-no leaves

Tundra

Very dry, cooler temps; extremely cold in winter

Permafrost

Lichens, scrubby vegetation

Taiga(Boreal Forest)

Small evergreens

Long cold winters, short cool summers, moderate rain

Chaparral

Mild wet winters, warm dry summers.

Mediterranean climate

Frequent fires

World’s Biomes