L19: Species Interactions - Predation and Herbivory

predation

an individual of one species (consumer) eats individuals of another species (prey/plants)

predation includes both

animals and plants as predators

intraguild predation

predator eats another predator

omnivory

predator is animal or plant and prey is animals and plants

herbivory

predator is animal and prey is plant/alga

parasitism

predator is parasite and prey is host

What is the difference between lethality of consumption in prey and plants?

any prey consumption lethal, plants can tolerate large amounts of consumption (unless young plant, clonal animals)

What is the difference between consumption avoidance strategies between prey and plants?

prey move away/hiding behaviors, plants are sedentary and use different defensive strategies

What are some physical difference between prey and plants that affect how they evolved to avoid consumption?

animal tissue different than plant tissue, plant have cell walls and lower in nutrition, animals have symbiotic relationships with gut microbes to digest cellulose

What is the difference in how predators and herbivores choose food to eat?

predators are generalists, herbivores are specialists (specific species or parts of plants they eat)

What are the differences in what predators and herbivores have to focus on in terms of consumption?

predators focus on eating, herbivores and prey must focus on eating and not being eaten

What limits predators? Prey?

predators limited by amount of prey, prey limited by plants/food and predators

corsorial hunting

pursue prey until preey cannot run anymore, kill it

sit-and-wait ambush hunting

hide/stalk prey, pounce to catch it

Examples of corsorial hunting

cheetah stalks and pounces/chases prey until it catches it

What morphology do prey use to prevent being eaten?

larger body size, weaponry, armor

What behavior do prey use to prevent being eaten?

hiding/refuge use, spatiotemporal change in habitat, schooling, vigilance

crypsis

strategy to avoid detection by predators by either blending in with surroundings or mimicry of sound or smells of other animals to deter predator

What physiology do prey use to avoid being eaten?

toxins, aposematic warning (bright colors to signal danger)

learned avoidance

predator eats a poisonous animal and dies or gets very sick, future offspring learn not to eat them

mimicry example

Viceroy butterfly mimics the color and pattern of the toxic monarch butterfly to avoid being eaten without having to use energy to evolve toxicity itself

resistance

plant defense against herbivores

tolerance

plant compensation against herbivore damage

What are the types of chemical defenses plants use?

secondary compounds/metabolites (poisons, endocrine disruptors), bad tastes, plant volatiles (secrete chemicals to deter herbivores, attract predators of the herbivores, warn other plants)

What are the physical defenses of plants?

spines, thorns, hairs, thick bark, waxy leaves

constitutive defenses

permanent defenses, always “on”, active prior to attack

inducible defenses

defenses activated by attack

Example of constitutive defense

acacia trees always have thorns whether it is being attacked or not, thorns are reduced if no herbivory pressure (related to inducible)

plant tolerance

compensation/overcompensation to herbivory OR ability to mitigate negative fitness effects of herbivory

What are some examples of plant tolerance?

more photosynthesis in undamaged parts of plant, compensatory growth to damaged parts, utilized stored resources for regrowth, reallocate resources to unattacked parts, increase nutrient uptake, change plant architecture (e.g. more energy to root growth if roots are safe)

How do herbivores overcome plant defenses?

using gut microbe symbiotic relationships, digestive enzymes to tolerate chemical defenses, morphology adaptations to avoid defenses (e.g. giraffes have long tongue to eat leaves around acacia thorns)

Lokta-Volterra Predator-Prey Models describe what

how predator and prey populations interact to alter the other’s abundance

What are the two equations for the Lokta-Volterra Predator-Prey Model and what do the variables stand for?

dN/dt = rN - αNP and dN/dt = rN (without predators)

N - prey population

P - predator population

α - efficiency of prey capture

As predator popuation increases then

prey population decreases (and vice versa)

As both predator and prey populations increase then

the frequency of interaction increases

What do the following equations talk about and what do the variables represent?

dP/dt = -mP

dP/dt = -mP + baNP

first equation has no prey, second equation includes prey

m - mortality rate

a - efficiency of prey capture

b - number of offspring

When there is no change in prey growth aNP =

0 because this represents the number of prey killed

What equation can you use (derived from previous equations) to measure how many predators for no prey population growth?

P = r/a

What equation can you use (derived from previous equations) to measure how many prey for no predator population growth?

N = m/ba

Describe how predator and prey populations interact and change.

predators rely on prey for food, predator birth rate and population density increase, prey are killed and prey population decreases, decreased prey means decreased predator population, decreased predator population means increased prey population, loop