1. Species Interactions in Communities

2. Types of Interactions (type of impact on each species in parentheses)
Competition ( - , - )
interspecific vs. intraspecific
Predation ( + , - )
carnivory or herbivory
Parasitism (+ , - )
Commensalism ( + , 0 )
Mutualism ( + , + )

3. The Competitive Exclusion Principle
If two species, with the same niche (job/role), 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

4. Impacts of Competition
Species B

5. Resource Partitioning
Ruddy turnstone searches under shells and pebbles
for small invertebrates
Resource Partitioning
Herring gull
is a tireless
scavenger
Brown pelican dives for fish, which it locates from the air
Avocet sweeps bill through mud and surface water in search of small crustaceans, insects, and seeds
Dowitcher probes
deeply into mud in
search of snails,
marine worms, and
small crustaceans
Black skimmer
seizes small fish
at water surface
Flamingo feeds on
minute organisms
in mud
Figure 4.5: Specialized feeding niches of various bird species in a coastal wetland. This specialization reduces competition and allows sharing of limited resources.
Louisiana heron
wades into water
to seize small fish
Oystercatcher feeds on
clams, mussels, and other
shellfish into which it
pries its narrow beak
Piping plover feeds on insects and tiny crustaceans on sandy beaches
Scaup and other diving
ducks feed on mollusks,
crustaceans, and aquatic
vegetation
Knot (sandpiper)
picks up worms
and small crustaceans
left by receding tide
Environmental Science: Problems, Concepts, and Solutions. (12th ed.) by G. Tyler Miller, Jr. and Scott Spoolman

6. Black-throated Green Warbler Yellow-rumped Warbler
Resource Partitioning
Blakburnian Warbler
Black-throated Green Warbler
Cape May Warbler
Bay-breasted Warbler
Yellow-rumped Warbler
Figure 6.4: Sharing the wealth: resource partitioning of five species of insect-eating warblers in the spruce forests of the U.S. state of Maine. Each species minimizes competition for food with the others by spending at least half its feeding time in a distinct portion (shaded areas) of the spruce trees, and by consuming somewhat different insect species.
(After R. H. MacArthur, “Population Ecology of Some Warblers in Northeastern Coniferous Forests,” Ecology 36 (1958): 533–536)
Environmental Science: Problems, Concepts, and Solutions. (12th ed.) by G. Tyler Miller, Jr. and Scott Spoolman

7. Purple Martin & Starling
Interspecific competition
Starlings tend to fight off Martins, kill nestlings, and break their eggs

8. Red & Grey Squirrels Interspecific competition
The Grey Squirrel (Sciurus carolinensis) was introduced to Britain in about 30 sites between 1876 and 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
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.
Red Squirrel Range

9. Africanized & European HB
Interspecific competition
AHB mature faster and are more opportunistic feeders

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

11. Speaking of Bees… EHB larvae with a parasitic mite on it Host = EHB
Parasite = mite
Example of ectoparasite

12. Elk and Liver Fluke Parasitism Elk = host Fluke = parasite
Example of an endoparasite

13. Liver Fluke Life Cycle
Many endoparasites may have a cyst form or occupy intermediate hosts that they may not harm…

14. Impacts of Predation

15. Lion & Zebra Carnivory predation Zebra-prey Lions-predator
* While individual zebras are harmed, the prey population benefits by loss of old and sick members

16. 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!

17. 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.

18. Commensalism vs. Mutualism
How do you decide?

19. Shark & Remora Commensalism or mutualism? Depends…
If remora gets transport, protection and scraps and shark nothing ( +, 0 )
If shark has parasites removed by remora ( +, + )

20. Oak & Mycorrhizae Fungi
Mutualism
Oak tree provides sugars for fungi
Fungi absorbs moisture and nutrients for tree

21. Lichen (algae & fungus)
Tricky?
Mutualism (self)
Commensalism (with living tree)

22. Eastern Lamp Mussel & Largemouth Bass
Commensalism: Glochidia (larvae) live on fish gills for about a month…

23. Speaking of Eastern Lamp Mussels…
Carnivory predation by herons

24. More on Eastern Lamp Mussels…
Interspecific competition with Zebra Mussels
Zebra Mussels are also nonnatives from Europe that arrived in ship’s ballast tanks

25. Spread of Zebra Mussels (good example of a accidentally introduced nonnative species)

26. Epiphytes and Trees Spanish Moss Commensalism
Epiphyte roots on bark and has better access to light and water--no harm to tree

27. More Epiphytes…
A common site on tropical or temperate rain forest trees

28. 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

29. Quiz Time

30. You decide!
Herbivory predation or
Mutualism?
MUTUALISM!

31. You decide!
Easy?
HERBIVORY PREDATION!

32. You decide! A hermit crab with an anemone attached to the shell…
MUTUALISM!

33. You decide! A Tobacco Hornworm covered with wasp pupae… ECTOPARASITE!
Adult: Carolina Sphinx Moth
A Tobacco Hornworm covered with wasp pupae…
ECTOPARASITE!

34. You decide!
Mistletoe?
ECTOPARASITE!

35. So…species must:
Adapt (in other words, coevolve due to competition, predation, or develop symbiosis)
Migrate (run away)
Die (go extinct)