Predation & Herbivory

1. Predation & Herbivory Photo of acorns & weevil grub from http://www.insectimages.org/browse/detail.cfm?imgnum=0014201

2. Exploitation (+/- or antagonistic interaction) Predators (active foragers, ambush predators, sit-and-wait predators, etc.) generally kill and consume prey Photo of ants dismembering a cicada from Wikimedia Commons

3. Exploitation (+/- or antagonistic interaction) 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) Photo of leaf-miner damage to a leaf from Wikimedia Commons

4. Exploitation (+/- or antagonistic interaction) Parasites (internal [endoparasite], external [ectoparasite], etc.) consume tissues or fluids of theirs hosts, generally without killing them Photo of human head louse from Wikimedia Commons

5. Exploitation (+/- or antagonistic interaction) 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 Photo of phorid fly ovipositing (laying eggs) into a honey bee from Wikimedia Commons

6. Exploitation (+/- or antagonistic interaction) Pathogens Parasites that cause disease (which manifests as pain, dysfunction or death) Photomicrograph of an Ebola virion (a complete virus particle) from Wikimedia Commons

7. Prey Switching Guppies preferentially eat whichever prey is most common (aquatic tubificid worms vs. fruit flies) Cain, Bowman & Hacker (2014), Fig. 13.5, after Murdoch et al. (1975)

8. Apparent Competition Robert Holt H - - + + P P - Solid arrows indicate direct effects, dotted arrows indicate indirect effects Original idea from Holt (1977); figure redrawn from Menge (1995) & Morin (1999); photo of Holt from http://people.biology.ufl.edu/rdholt/

9. 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 aNPis 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 ais exemplified by a baleen whale eating krill, small aby a spider catching flies in its web aNis 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

10. Functional Response Curves Why might functional responses have these shapes? Satiation Rate of prey capture Host-switching, developing a search image, etc. Victim abundance (V) Prey abundance (N) Figure from Gotelli (2001), after Holling (1959)

11. 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 mis the per capitamortalityrate Positive population growth occurs when prey are present: dP/dt = baNP- mP bis the conversion efficiency – the ability of predators to turn a prey item into per capita growth Large bis exemplified by a spider catching flies in its web (or wolves preying on moose), small bby a baleen whale eating krill baNreflects the numerical response of the predator population – the per capita growth rate of the predator pop. as a function of the prey pop.

12. Equilibrium solution: For the prey (N) population: dN/dt= rN- aNP 0 = 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 ^ Prey (N) Figure from Gotelli (2001)

13. 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 Ndepends on the ratio of the death rate of predators to the conversion & conversion efficiencies of predators ^ m/ba Prey (N) Figure from Gotelli (2001)

14. 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) Figure from Gotelli (2001)

15. 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 Figure from Gotelli (2001)

16. Huffaker’s mites 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 Cain, Bowman & Hacker (2014), Fig. 13.20, after Huffaker (1958)

17. Huffaker’s mites Vaseline barriers around oranges created prey refuges; herbivorous mites could balloon - via silk strands - among oranges; predators & preycoexisted with coupled, cyclicaldynamics Cain, Bowman & Hacker (2014), Fig. 13.20, after Huffaker (1958)

18. Adaptations of Prey Mimicry (e.g., crypsis, false-advertisement, etc.) Physical defenses (e.g., large size, rapid or agile movements, body armor, spines, etc.) Toxins (often accompanied by aposematic coloration) Photos of porcupine, lionfish, Draco lizard & snake-mimic caterpillar from Wikimedia Commons

19. Counter-adaptations of Predators Mimicry (e.g., camouflage, etc.) Detection & prey-capture prowess (e.g., heightened sensory capabilities, etc.; speed, agility, fangs, claws, etc.) Poison (e.g., venom, etc.) Photos of owl, cobra & orchid mantis from Wikimedia Commons

20. Adaptations of Plants Defenses (e.g., structural, chemical [e.g., secondary compounds], inducible, etc.) Avoidance (e.g., masting, etc.) Tolerance (e.g., compensation, etc.) Photo of acorn mast – http://blog.chron.com/lazygardener/2012/11/of-course-its-raining-acorns-its-a-masting-year; photos of grazing sheep & raspberry thorns, as well as structure of caffeine, from Wikimedia Commons

21. Counter-Adaptations of Herbivores Behavioral (e.g., consumption of clay, etc.) Structural (e.g., teeth, etc.) Chemical (e.g., clay, digestive enzymes, etc.) Photos of horse’s teeth from Wikimedia Commons; photo of macaws at clay lick from http://surbound-birding.blogspot.com/2013/04/macaw-and-parrot-clay-licks-in.html