Presentation on species interactions that determine a species' niche and impact population dynamics. Class notes from November 5th, 2012.

1. Species Interactions in
Communities
A good look at coevolution at work
in our world…

2. Types of Interactions
(type of impact on each species in parentheses)
• Competition ( - , - )
– interspecific vs. intraspecific
• Predation ( + , - )
– Carnivory (true) or herbivory
– Parasitism, pathogens, parasitoids
• Commensalism ( + , 0 )
• Mutualism ( + , + )
• Amensalism ( - , 0 )
*Note some texts list parasitism as a separate interaction

3. The Competitive Exclusion
Principle
If two species, with the same niche,
coexist in the same ecosystem, then
one will be excluded from the niche 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. Visualizing Impacts of Competition
Species B

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

6. 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.
Grey Squirrel Range • 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.
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,
Red Squirrel Range published records and a few additions up to 1997.

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

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

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

10. Resource Partitioning
Blakburnian Black-throated Cape May Bay-breasted Yellow-rumped
Warbler Green Warbler Warbler Warbler Warbler
Environmental Science: Problems, Concepts, and Solutions. (12th ed.) by G. Tyler Miller, Jr. and Scott Spoolman

11. Impacts of Predation

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

13. 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!
*see on YouTube

14. 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.

15. Other forms of predation…
• Parasites (endo and ecto)
– Live off host, but do not consume large
portion
• Pathogens
– Cause disease
– Viruses, bacteria, fungi, protists, some
worms
• Parasitoids (endo and ecto)
– Lay eggs in or on host & larve consume
host

16. Remember those EHBs…
• EHB larvae with a
parasitic mite on it
• Host = EHB
• Parasite = mite
• Example of
ectoparasite

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

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

19. Parasitoids
*another example on
YouTube

20. Commensalism vs. Mutualism
How do you decide?

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

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

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

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

25. Speaking of Eastern Lamp
Mussels…
• Carnivory predation
by herons

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

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

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

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

30. 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

31. Quiz Time

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

33. You decide!
Easy?
HERBIVORY
PREDATION!

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

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

36. You decide!
Mistletoe? Not a
typical commensal
epiphyte, rather a
ECTOPARASITE!

37. One More…

38. 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.

39. 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?

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