1. Predation & Herbivory
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This beetle larva is an example of a seed predator (an herbivore that eats seeds).
Photo of acorns & weevil grub from

2. Pairwise Species Interactions
Influence of species A
- (negative)
0 (neutral/null)
+ (positive) A B
Competition - A B
Amensalism - A B
Antagonism
(Predation/Parasitism) + - - A B
Amensalism - A B
Neutralism
(No interaction) A B
Commensalism +
Influence of Species B
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Note that whereas +/- interactions are labeled “antagonism” in the table above, your textbook refers to these types of interactions as “exploitation.”
Abrahamson, Warren G., ed Plant-Animal Interactions. McGraw-Hill Publishing, New York, NY.
Morin, Peter J Community Ecology. Blackwell Science, Inc., Oxford, U.K. A B
Antagonism
(Predation/Parasitism) - + A B
Commensalism + A B
Mutualism + +
Redrawn from Abrahamson (1989); Morin (1999, pg. 21)

3. Exploitation (+/- interaction, a.k.a. antagonism)
Predators (active foragers, ambush predators, sit-and-wait predators, etc.)
generally kill and consume prey
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Wikipedia “Predation” page; accessed 09-X-2014
Photo of ants dismembering a cicada from Wikimedia Commons

4. Exploitation (+/- interaction, a.k.a. antagonism)
Herbivores (browsers, grazers, phloem suckers, seed predators, etc.)
eat tissues or fluids of plants or algae;
often quite specialized (w.r.t. species & plant part)
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Wikipedia “Herbivore” page; accessed 09-X-2014
Photo of leaf-miner damage to a leaf from Wikimedia Commons

5. Exploitation (+/- interaction, a.k.a. antagonism)
Parasites (internal [endoparasite], external [ectoparasite], etc.)
consume tissues or fluids of their hosts,
generally without killing them
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Wikipedia “Parasitism” page; accessed 09-X-2014
Photo of human head louse from Wikimedia Commons

6. Exploitation (+/- interaction, a.k.a. antagonism)
Parasitoids
Insects that lay an egg or eggs on or in a host (generally an insect or spider);
the larvae eat and usually kill the host
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See Fig in textbook – parasitoids could be considered both parasites and carnivores.
Photo of phorid fly ovipositing (laying eggs) into a honey bee from Wikimedia Commons

7. Exploitation (+/- interaction, a.k.a. antagonism)
Pathogens
Parasites that cause disease
(which manifests as pain, dysfunction or death)
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Wikipedia “Ebola virus disease” page; accessed 09-X-2014
This example illustrates that parasites can be living organisms or infectious non-living particles (such as viruses).
Photomicrograph of an Ebola virion (a complete virus particle) from Wikimedia Commons

8. Predator Generally Experiences Net Benefit,
but not always!
Fire ant latched onto mandible of ant lion,
fire ant died, prevented ant lion from building pit,
and ant lion starved to death
Please do not use the images in these PowerPoint slides without permission.
On average the predator receives a net benefit (+), whereas the prey receives a net cost (-), but that means that sometimes an interaction between one individual predator animal and one individual prey animal will end up as a minus-minus interaction (see illustration in PowerPoint slide).
Lucas, Jeffrey R. & H. Jane Brockman Predatory behavior between ants and antlions (Hymenoptera: Formicidae and Neuroptera: Myrmeeontidae). Journal of the Kansas Entomological Society 54:
K. Harms’s photo of ant lion pit (Kisatchie Nat’l. Forest, LA); figure from Lucas & Brockman (1981)

9. Prey Switching
Guppies preferentially eat whichever prey is most common (aquatic tubificid worms vs. fruit flies);
owing to development of search image or learning to efficiently handle the prey
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Murdoch, W. W. et al Switching in a predatory fish. Ecology 56:
Bowman, Hacker & Cain (2017), Fig. 12.6, after Murdoch et al. (1975)

10. Apparent Competition Robert Holt H P P- - + + P - P
Solid arrows indicate direct effects,
dotted arrows indicate indirect effects
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For this figure I am using P=plant & H=herbivore.
Holt, R. D Predation, apparent competition, and the structure of prey communities. Theoretical Population Biology 12:
Menge, Bruce A Indirect effects in marine rocky intertidal interaction webs: Patterns and importance. Ecological Monographs 65:21-74.
Morin, Peter J Community Ecology. Blackwell Science, Inc., Oxford, U.K.
Original idea from Holt (1977); figure redrawn from Menge (1995) & Morin (1999);
photo of Holt from

11. Lotka-Volterra Predator-Prey Models
Prey in the absence of predators:
dN/dt = rN
Prey in the presence of predators:
dN/dt = rN - aNP
where aNP is loss to predators
Losses to predators are proportional to NP (random encounters) and a (capture efficiency – effect of a single predator on the per capita growth rate of the prey population)
Large a is exemplified by a baleen whale eating krill, small a by a spider catching flies in its web
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See: Gotelli, Nicholas J A Primer of Ecology, 3rd ed. Sinauer Assocs., Inc., Sunderland, MA.
aN is the functional response of the predator (rate of prey capture as a function of prey abundance); in this case linear, i.e., prey capture increases at a constant rate as prey density increases

12. Functional Response Curves
Why might functional responses have these shapes?
Satiation
Rate of prey capture
Please do not use the images in these PowerPoint slides without permission.
Gotelli, Nicholas J A Primer of Ecology, 3rd ed. Sinauer Assocs., Inc., Sunderland, MA.
Holling, C. S The components of predation as revealed by a study of small mammal predation of the European pine sawfly. The Canadian Entomologist 91:
Host-switching, developing a search image, etc.
Victim abundance (V)
Prey abundance (N)
Figure from Gotelli (2001), after Holling (1959)

13. Lotka-Volterra Predator-Prey Models
In the model’s simplest form, the predator is specialized on 1 prey species; in the absence of prey the predator pop. declines exponentially:
dP/dt = -mP
P is the predator pop. size, and m is the per capita mortality rate
Positive population growth occurs when prey are present:
dP/dt = baNP - mP
b is the conversion efficiency – the ability of predators to turn a prey item into per capita growth
Large b is exemplified by a spider catching flies in its web (or wolves preying on moose), small b by a baleen whale eating krill
Please do not use the images in these PowerPoint slides without permission.
See: Gotelli, Nicholas J A Primer of Ecology, 3rd ed. Sinauer Assocs., Inc., Sunderland, MA.
baN reflects the numerical response of the predator population – the per capita growth rate of the predator pop. as a function of the prey pop.

14. Equilibrium solution: For the prey (N) population: dN/dt = rN - aNP
aNP = rN
aP = r
P = r/a
dN/dt < 0
dN/dt = 0 ^
Predators (P)
r/a
The prey isocline
P depends on the ratio of the growth rate of prey to the capture efficiency of the predator
dN/dt > 0 ^
Please do not use the images in these PowerPoint slides without permission.
Gotelli, Nicholas J A Primer of Ecology, 3rd ed. Sinauer Assocs., Inc., Sunderland, MA.
Prey (N)
Figure from Gotelli (2001)

15. Equilibrium solution: For the predator (P) population:
dP/dt = baNP - mP
0 = baNP - mP
baNP = mP
baN = m
N = m/ba
dP/dt < 0
dP/dt > 0 ^
Predators (P)
The predator isocline
N depends on the ratio of the death rate of predators to the capture and conversion efficiencies of predators ^
Please do not use the images in these PowerPoint slides without permission.
Gotelli, Nicholas J A Primer of Ecology, 3rd ed. Sinauer Assocs., Inc., Sunderland, MA.
m/ba
Prey (N)
Figure from Gotelli (2001)

16. Combined graphical solution in state space:
The predator and prey populations cycle because they reciprocally control one another’s growth
Predators (P)
r/a
m/ba
Prey (N)
Please do not use the images in these PowerPoint slides without permission.
Gotelli, Nicholas J A Primer of Ecology, 3rd ed. Sinauer Assocs., Inc., Sunderland, MA.
Figure from Gotelli (2001)

17. Combined graphical solution in state space:
The predator and prey populations cycle because they reciprocally control one another’s growth
Predators (P)
r/a
m/ba
Prey (N)
Prey
Please do not use the images in these PowerPoint slides without permission.
Gotelli, Nicholas J A Primer of Ecology, 3rd ed. Sinauer Assocs., Inc., Sunderland, MA.
Figure from Gotelli (2001)

18. Huffaker’s mites – predator-prey cycles in the lab
Oranges & rubber balls
in experimental arena
Herbivorous mite’s population increased until addition of a predatory mite;
predator drove herbivore to extinction, then itself declined to extinction
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Huffaker, Carl B Experimental Studies on Predation: Dispersion Factors and Predator- Prey Oscillations. Hilgardia: A Journal of Agricultural Science 27:
Bowman, Hacker & Cain (2017), Fig , after Huffaker (1958)

19. Huffaker’s mites – predator-prey cycles in the lab
Vaseline barriers around oranges created prey refuges;
herbivorous mites could balloon - via silk strands - among oranges;
predators & prey coexisted with coupled, cyclical dynamics
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Note: Huffaker also added wooden dowels to the oranges, atop which the ballooning prey mites could spin silk threads to catch air currents and disperse.
Huffaker, Carl B Experimental Studies on Predation: Dispersion Factors and Predator- Prey Oscillations. Hilgardia: A Journal of Agricultural Science 27:
Bowman, Hacker & Cain (2017), Fig , after Huffaker (1958)

20. Top-down vs. bottom-up influences
Population Cycles
Top-down vs. bottom-up influences
on snowshoe hare abundance
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The trophic hierarchy shows both predation and herbivory; predator-prey interactions influence hare populations via top-down impact, whereas herbivore-plant interactions influence hare populations via bottom-up impact.
See the lynx and snowshoe hare case study in your textbook for details on the complex interplay among trophic levels and involving the ecology of fear that together determine the population cycles of hares, along with the combination of field observations, experiments (sometimes very large scale), and quantitative modeling that scientists have used to infer the underlying causes of these cyclical dynamics.
Charles J. Krebs Of lemmings and snowshoe hares: the ecology of northern Canada. Proceedings of the Royal Society B. 278:
Photo of lynx from “Lynx” Wikipedia page; downloaded 2/12/2018.
Photo of snowshoe hare from “Snowshoe hare” Wikipedia page; downloaded 2/12/2018.
Photo of dwarf birch from “Dwarf birch” Wikipedia page; downloaded 2/12/2018.
Figure from Krebs (2011); photos from Wikimedia Commons

21. Adaptations of Prey Physical defenses
(e.g., large size, rapid or agile movements, body armor, spines, etc.)
Poisons / Toxins
(often accompanied by aposematic [warning] coloration)
Mimicry
(e.g., crypsis, false-advertisement, etc.)
Please do not use the images in these PowerPoint slides without permission.
Note: It’s a bit of a chicken-or-egg problem in terms of adaptations and counter-adaptations. We also need to be careful we are not telling “Just So Stories”; See: Gould, S. J. & R. C. Lewontin The spandrels of San Marco and the Panglossian paradigm: a critique of the adaptationist programme. Proceedings of the Royal Society of London, Series B 205:
Wikipedia “Porcupine” page; accessed 08-X-2014
Wikipedia “Pterois” page (re-directed from “Lionfish”); accessed 08-X-2014
Wikipedia “Crypsis” page; accessed 09-X-2014
Wikipedia “Mimicry” page; accessed 08-X-2014
Photos of porcupine, lionfish, Draco lizard & snake-mimic caterpillar from Wikimedia Commons

22. Counter-adaptations of Predators Detection & prey-capture prowess
(e.g., heightened sensory capabilities, etc.; speed, agility, fangs, claws, etc.)
Poisons / Toxins
(e.g., venom, etc.)
Mimicry
(e.g., camouflage, etc.)
Please do not use the images in these PowerPoint slides without permission.
Note: It’s a bit of a chicken-or-egg problem in terms of adaptations and counter-adaptations. We also need to be careful we are not telling “Just So Stories”; See: Gould, S. J. & R. C. Lewontin The spandrels of San Marco and the Panglossian paradigm: a critique of the adaptationist programme. Proceedings of the Royal Society of London, Series B 205:
Wikipedia “Owl” page; accessed 09-X-2014
Wikipedia “Cobra” page; accessed 09-X-2014
Wikipedia “Hymenopus coronatus” (redirected from “Orchid mantis”) page; accessed 09-X-2014
Photos of owl, cobra & orchid mantis from Wikimedia Commons

23. Adaptations of Plants Avoidance (e.g., masting, etc.) Tolerance
(e.g., compensation, etc.)
Defenses
(e.g., structural, chemical [e.g., secondary compounds], inducible, etc.)
Please do not use the images in these PowerPoint slides without permission.
Note: These various adaptations provide some of the reasons that herbivores are often quite specialized in their host-plant preferences (since they are often only able to deal with certain types of defenses). It’s also a bit of a chicken-or-egg problem in terms of adaptations and counter-adaptations, i.e., which came first? We also need to be careful we are not telling “Just So Stories”; See: Gould, S. J. & R. C. Lewontin The spandrels of San Marco and the Panglossian paradigm: a critique of the adaptationist programme. Proceedings of the Royal Society of London, Series B 205:
Wikipedia “Grazing” page; accessed 09-X-2014
Wikipedia “Plant defense against herbivory” page; accessed 09-X-2014
Compensation – removal of plant tissue stimulates productive of new tissue
Masting – synchronous production of seeds, potentially to satiate seed predators
Photo of acorn mast –
photos of grazing sheep & raspberry thorns, as well as structure of caffeine, from Wikimedia Commons

24. Counter-Adaptations of Herbivores
Structural
(e.g., teeth, etc.)
Chemical
(e.g., clay, digestive enzymes, etc.)
Behavioral
(e.g., consumption of clay, etc.)
Please do not use the images in these PowerPoint slides without permission.
Note: It’s a bit of a chicken-or-egg problem in terms of adaptations and counter-adaptations. We also need to be careful we are not telling “Just So Stories”; See: Gould, S. J. & R. C. Lewontin The spandrels of San Marco and the Panglossian paradigm: a critique of the adaptationist programme. Proceedings of the Royal Society of London, Series B 205:
Wikipedia “Horse teeth” page; accessed 09-X-2014
Photos of horse’s teeth from Wikimedia Commons; photo of macaws at clay lick from