Species Interactions in Communities

A good look at coevolution at work in our world…

Types of Interactions(type of impact on each species in parentheses)

• Competition ( - , - )– interspecific vs. intraspecific

• Predation ( + , - )– carnivory or herbivory

• Parasitism (+ , - )• Commensalism ( + , 0 )• Mutualism ( + , + )• Amensalism ( - , 0 )

The Competitive Exclusion Principle

If two species, with the same niche, coexist in the same ecosystem, then one will be excluded from the community due to intense competition

• both species suffer so ( -, - )• losers usually migrate or die

or • this leads to resource partitioning and species

assume smaller realized niches since they cannot occupy their full fundamental niches

Impacts of Competition

Species B

Fig. 4-5, p. 68

Louisiana heronwades into waterto seize small fish

Black skimmerseizes small fishat water surface

Ruddy turnstone searches

under shells and pebbles

for small invertebratesAvocet sweeps bill

through mud and surface water in search of small crustaceans, insects, and seeds

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

Dowitcher probesdeeply into mud insearch of snails,marine worms, andsmall crustaceans

Herring gullis a tirelessscavenger

Flamingo feeds onminute organismsin mud

Scaup and other divingducks feed on mollusks,crustaceans, and aquaticvegetation

Piping plover feeds on insects and tiny crustaceans on sandy beachesKnot (sandpiper)

picks up wormsand small crustaceansleft by receding tide

Oystercatcher feeds onclams, mussels, and othershellfish into which itpries its narrow beak

Resource Partitioning

Environmental Science: Problems, Concepts, and Solutions. (12th ed.) by G. Tyler Miller, Jr. and Scott Spoolman

Fig. 6-4, p. 112

Cape May Warbler

Blakburnian Warbler

Black-throated Green Warbler

Yellow-rumped Warbler

Bay-breasted Warbler

Resource Partitioning

Environmental Science: Problems, Concepts, and Solutions. (12th ed.) by G. Tyler Miller, Jr. and Scott Spoolman

Purple Martin & Starling

• Interspecific competition

• Starlings tend to fight off Martins, kill nestlings, and break their eggs

Red & Grey Squirrels• Interspecific competition• The Grey Squirrel (Sciurus

carolinensis) was introduced to Britain in about 30 sites between 1876 and 1929. It has easily adapted to parks and gardens replacing the red squirrel.

• The Red Squirrel (Sciurus vulgaris) is native to Britain but its population has declined due to competitive exclusion, disease and the disappearance mature conifer forests in lowland Britain.

Grey Squirrel Range

Red Squirrel Range

Maps prepared by the Biological Records Centre, CEH Monks Wood, from records collated by the Mammal Society and others mainly between 1965 and 1993, also including earlier,

published records and a few additions up to 1997.

Africanized & European HB

• Interspecific competition

• AHB mature faster and are more opportunistic feeders

Spread of AHB(also good example of a nonnative species)

Speaking of Bees…

• EHB larvae with a parasitic mite on it

• Host = EHB• Parasite = mite• Example of

ectoparasite

Elk and Liver Fluke

• Parasitism• Elk = host• Fluke = parasite• Example of an

endoparasite

Liver Fluke Life Cycle

• Many endoparasites may have a cyst form or occupy intermediate hosts that they may not harm…

Impacts of Predation

Lion & Zebra

• Carnivory predation• Zebra-prey• Lions-predator

* While individual zebras are harmed, the prey population benefits by loss of old and sick members

Rough-Skinned Newt & Common Garter Snake

• Carnivory predation• Newt-prey

– Has genes to produce potent toxins which discourage predation

• Snake-predator– Has genes for resistance to newt

toxin

* Results in an “evolutionary arms race”… coevolution!

Monarch Butterfly & Milkweed

• Herbivory predation• Milkweed-prey (defense)

– Latex: A milky white sap that becomes sticky and coagulates when exposed to air.

– Cardiac glycoside: To various degrees, it is toxic to herbivores with hearts (birds and mammals). Monarchs and several other arthropods that eat milkweed have a tolerance for cardiac glycosides, although evidently not at the high levels found in some milkweed species.

• Butterfly-predator– Monarch larve cut the petiole of the

leaf before beginning to eat it. This "leaf-notching" behavior cuts off the supply of latex.

Commensalism vs. Mutualism

How do you decide?

Shark & Remora

• Commensalism or mutualism?

• Depends…– If remora gets

transport, protection and scraps and shark nothing ( +, 0 )

– If shark has parasites removed by remora ( +, + )

Oak & Mycorrhizae Fungi

• Mutualism• Oak tree provides

sugars for fungi• Fungi absorbs

moisture and nutrients for tree

Lichen (algae & fungus)

• Tricky?• Mutualism (self)• Commensalism

(with living tree)

Eastern Lamp Mussel & Largemouth Bass

Commensalism: Glochidia (larvae) live on fish gills for about a month…

Speaking of Eastern Lamp Mussels…

• Carnivory predation by herons

More on Eastern Lamp Mussels…

• Interspecific competition with Zebra Mussels

• Zebra Mussels are also nonnatives from Europe that arrived in ship’s ballast tanks

Spread of Zebra Mussels(good example of a accidentally introduced

nonnative species)

Epiphytes and Trees

• Spanish Moss• Commensalism• Epiphyte roots on

bark and has better access to light and water--no harm to tree

More Epiphytes…

• A common site on tropical or temperate rain forest trees

Humans and E. coli Bacteria

• Mutualism• Humans provide

food and shelter (large intestine) for the bacteria

• E. coli assist in human digestion and provide Vitamin K for host

Quiz Time

You decide!

Herbivory predation orMutualism?

MUTUALISM!

You decide!

Easy?

HERBIVORYPREDATION!

You decide!

A hermit crab with an anemone attached to the shell…

MUTUALISM!

You decide!

A Tobacco Hornworm covered with wasp pupae…

ECTOPARASITE!

Adult: Carolina Sphinx Moth

You decide!

Mistletoe?

ECTOPARASITE!

One More…

Ammensalism• One species is hurt, but the

other does not benefit ( -, 0 )• No apparent coevolutionary

relationship (one way process)

• Example: As wild pigs forage, they often disturb the upper layer of soil and many organisms may be taken from their burrows and exposed to predation by the action of the pigs, although the harm that the burrowers suffer does not improve the pig's situation at all.

Black Walnut & Azalea

• Example of alleopathy (not in your text)

• Black Walnut secretes chemical (juglone) that inhibits growth of other plants like azalea

• Could be ammensalism, competition, or avoidance of predation?

So…species must:

• Adapt (in other words, coevolve due to competition, predation, or develop symbiosis)

• Migrate (run away)

• Die (go extinct)