Lecture 29: Species interactions: Predator avoidance, mimicry and symbiosis
1. Predator avoidance: examples
a. Behavior can deter or fool predators (see also Fig. 53.4)
i. grass snake plays dead
ii. puffer fish
iii. bombardier beetle (plus a little chemistry!)
b. Appearance can conceal (camouflage or crypticity, see also Fig. 53.5))
i. bittern (behavior too)
ii. cuckoo egg
iii. leafhoppers
iv. sloth
c. Appearance can startle or deceive
i. frog eyespots
ii. butterfly eyespots (Fig. 53.6)
d. Appearance can advertise unpleasantness (aposematic coloration-- often yellow or orange and black, but also see Fig. 53.7))
i. poison arrow frog
ii. poisonous caterpillars
iii. bees and wasps
iv. monarch butterfly
2. Mimicry is a complex resemblance to something else that is evolved by natural selection
a. Crypticity (camouflage) is mimicry of surroundings-- species evolves resemblance to background
b. Mimicry of dangerous species also occurs
i. Batesian mimicry: harmless organism (the mimic) evolves to resemble a dangerous one (the model) Fig. 53.8
ii. Mullerian mimicry: dangerous organisms evolve to resemble one another
3. Batesian mimicry: palatable species mimics a dangerous or noxious one
a. Predators that experience the dangerous species learn to avoid it due to aposematic (warning) coloration -- they will stay away from similar looking organisms, even if they are harmless
b. The model must be more abundant than the mimic, or the predator will unlearn the avoidance
c. Batesian mimicry is advantageous to the mimic but not to the model.
d. Natural selection favors mimics that look most like the models, but favors models that are different from the mimics.
4. Mullerian mimicry: convergence of distasteful species to the same phenotype
a. individuals of all species within the mimicry complex benefit when a predator eats any of the species with similar phenotype.
b. all mimics benefit-- this is a mutualism
5. Mimicry examples
a. Batesian mimics: coral snake, moth
b. Mimicry complexes in butterflies - both Batesian and Mullerian
c. Monarch/viceroy -- Mullerian!
6. Symbiosis -- living together can be advantageous!
a. Mutualism. Both partners of an interaction benefit (see also 53.15)
i. Lichen-- algae plus fungus
ii. pollinators/plants
iii.clownfish
iv. corals and algal symbionts (zooxanthellae)
b. Commensalism. One partner benefits with neutral effect on other
i. manatee and whale barnacles
ii. epiphytes on tropical plants
7. These intricate interactions between species are examples of coevolution, in which each species evolves in response to the other.
a. predators and prey
b. parasites and hosts
c. mutualists
Next time: Parasites and parasitoids!