EX2 Eco Ch 14-15: Predation, Parasitism, & Mutualism Part 2

starting from slide 31

foraging considerations

(1) energy content - size & type of prey, (2) search time - time in patch, vulnerabilities, (3) handling time - capture, subdue, consume, (4) time for other activities - breeding

coevolution btwn predator and prey

predators exert selective pressure on prey → prey evolve defenses that increase prey fitness → prey exert selective pressure on predators → reduce predator fitness if can’t catch prey so more effective means of capturing evolve in predator

predatory defenses

(1) behavioral defenses - mobbing, alarm calls, group living, (2) protective armor - quills, thick shells, (3) chemical defenses - poisons, alarm pheromones

predatory defenses exs

cryptic coloration, object resemblance, flashing coloration, eyespot markings, warning coloration, Batesian mimicry, Mullerian mimicry

predatory defenses exs: cryptic coloration

body colors and patterns allow prey (or predators) to blend into surroundings

predatory defenses exs: object resemblance

common in insects

predatory defenses exs: flashing coloration

exhibit color patches when disturbed by predator, distracts or disorients predator

predatory defenses exs: eyespot markings

orients predator to less vulnerable body part

predatory defenses exs: warning coloration

bright colors, distinct patterns warn predator about prey & poisions, bad taste, etc.

predatory defenses exs: Batesian mimicry

animals evolve coloration that mimics warning colors of toxic species, coral snake = venomous but scarlet snake = nonvenomous

predatory defenses exs: Mullerian mimicry

unpalatable or venomous species share similar color patterns, predators learn to avoid all species with similar patterns

predator hunting methods

(1) ambush - lie in wait, frogs & alligators, minimal energy expense, (2) stalking - herons, high search time, (3) pursuit - lions & wolves, high handling time

parasitism

slow consumption, parasite benefits, host harmed

parasites

much smaller than host, highly specialized, reproduce more quickly and in larger numbers than host

parasitism & fitness

parasites fitness increases when close to host for long time for food, habitat, and dispersal, host fitness decreases by parasite from stunted growth, emaciation, behavior modification, sterility, and can die from secondary infection

parasitism population dynamics

parasites strongly influence pop. size and community structure, introduction of new parasite into host pop. w/ no defense can be severe (ex: Bubonic Plague - Yersinia pestis)

ectoparasites

live on outside of host, of vertebrates live in skin, feathers, scales, and hair (biting flies feed on birds and cause anemia and feather loss), of insects live on legs, upper/lower body surfaces, mouthparts (predatory mites feed on insects and their larvae)

endoparasites

live within the host, live under skin, in blood, in organs, in tissue (roundworms found in foxes and affect gastrointestinal tract)

plant parasites

use many different parts of a plant as habitat, live on roots and stems, penetrate roots and bark, live at root collar, live within leaves, live on flowers, pollen, or fruits (root-knot nematodes establish in plant roots and stunt plant growth)

parasitism: direct transmission

occurs through direct contact btwn infected host and uninfected individual, dispersal through air, water, or other substrate (ex: roundworms)

parasitism: intermediate vector

indirect transmission through intermediate vector/host (ex: mosquitoes, snails, mistletoe)

parasites regulate host pops.

for a parasite and host to coexist the host must fight infection without harming its own growth or reproduction, parasite needs to have an effect that allows it to survive, reproduce, and be transmitted without killing host, natural selection does not always favor peaceful coexistence of host and parasite, max fitness for parasite like host includes trade-offs

parasitism → mutualism/commensalism

if host countered negative effects of parasite → commensalism, if becomes beneficial → mutualism (ex: gut microbes were parasite and now aid in digestion) or obligate mutualism - more reciprocal exploitation than cooperation (ex: figs and fig wasps), can depend on environment (ex: trees and fungi, mutualist in nutrient poor soil and parasite in nutrient rich soil)

mutualism

positive interaction btwn 2 species that can be characterized by benefits like provision of essential resources (food, shelter), protection from predators, herbivores, and parasites, reduction of competition with third species, and enhanced reproduction

mutualism: degree of intimacy

(1) nonsymbiotic - free-living, ex: pollinators and flowering plants, (2) symbiotic - coexisting, obligate relationship, distinctions can blur, ex: lichen fused to single body

species interactions: key takeaways

(1) predation +/- ex: wolf-deer, immediate consumption, (2) parasitism +/- ex: tapeworm-human, intimate, prolonged interaction, (3) mutualism +/+ ex: bee-flower, reciprocal benefit