Bio Lab 5: Insect Predation

Structure of insect communities (2)

biotic interactions between generalist insect predators and their prey

generalist species

species with a broad ecological niche; species that are capable of surviving in a wide range of environment and can make use of various resources.

- feeding on any appropriately sized arthropod

3 feeding methods used by generalist insect predators

mandibles, raptorial forelegs, and unmodified legs

prey of generalist insect predators

usually consists of herbivorous insects

three potential prey species are simulated in the lab as;

three different types of candy

each simulations last how much time?

it lasts 15 seconds

how many rounds of simulations will there be?

6 to 8 rounds

3 type of generalist insect predators are modeled in the simulation as;

pair of fork, spoons, and knife.

pair of fork represents;

it represents grasping legs (dragonflies); unmodified

pair of spoons represents;

it represents raptorial legs (mantises)

pair of knife represents;

it represents mandibles (beetles)

prey reproduce based on;

they reproduce based on number remaining

predator numbers are;

they are adjusted to reflect mortality and reproduction.

in insect communities, prey species may develop;

they may evolve defenses like poison

the cost of defenses against predators for prey insects

slowed growth and reduced reproduction rate

how is the cost of evolutionary defense modeled in the simulation?

one prey type becomes poisonous, but suffers a lowered rate of reproduction.

in order to maintain all three predator types to prevent extinction of one species...

the predator type that suffer greatest mortality evolves to feed on poisonous prey species to...

3 stages of predation

search (recognition), pursuit (capture), handling

co-evolution

Process by which tight association of mutual selection pressures act on 2 or MORE species. It may happen with prey and predator in all stages of predation.

search

- predators search environment for acceptable prey

- searching stage ends with finding & recognizing suitable prey

predator adaptations to improve search success (4)

better visual & olfactory acuity, limiting searches to prey-rich habitats, quickly learning suitable prey types, avoid inedible species

learned avoidance

predators learning and recognizing poisonous or distasteful species by remembering harmful reactions from attempted predation events.

- improves foraging efficiency

- results in development of search image

search image

predator's method of identification of the most profitable and unprofitable prey. results from learned avoidance.

ex) Kestrels detecting the urine and feces of their prey.

pursuit

- predator chasing the prey; active hunting.

- happens after recognition stage

- ends with predator capturing the prey (physical contact).

predator adaptations to improve pursuit success (2)

locomotor adaptations (running, flight speed), highly coordinated behavior

predator adaptations to improve capture efficiency

improved motor skills, appendage modification

handling

- follows capture

- predator's attempt to not let prey escape

- efficiently subduing it and processing it

3 mechanism of processing prey

detoxification, eating, digesting.

limiting factor of predator's hunting time

time it takes for predator to eat and digest

4 characteristics of prey that natural selection favors

difficult to find, capture, subdue, and consume

Adaptations against predation (4)

coloration, behavior, morphology, physiology

defense of ladybird beetles (ladybugs)

chemical defense: they leave yellowish, strongly smelling fluid.

true or false; the recognition of potentially dangerous prey is innate.

false. it is not innate.

task for predators regarding profitable and unprofitable prey

they must learn to associate bad taste / illness with eating a species with memorable characteristics (search image)

the direction of selection prey exhibits in predator abundant environment

high effort in physical and chemical defense system that lowers growth and reproductive rate but gives advantage in protection.

consequence of one prey species becoming more toxic

only one predatory species can overcome its defenses.

example of co-evolution given in the prelab reading

predator species selecting more toxic prey so that it can specialize; prey species, in return, getting more toxic, and selects for predator species that can better overcome the toxicity.

mandibles

jaws; ground beetles, tiger beetles, ant lion larvae

- grasp and kill their prey

raptorial legs

enlarged from legs to grab and subdue prey; mantis, water bugs, ambush bugs

unmodified leg

not raptorial legs; commonly used by aerial predators to grasp prey with all of its legs; dragonflies, robber flies, scorpionflies

Batesian mimicry

non-toxic prey mimicking a toxic one to avoid predation

reason why poisonous prey does not grow exponentially

there are specialized predators that feed on poisonous prey & the cost of developing poisons

process in which poisonous prey acquire toxins

they consume toxins from plants they consume

intrinsic factors that constrain predator ability (3)

limited time available for prey searching, limited stomach size, time needed for digestion

extrinsic factors that constrain predator ability (2)

(inter/intra) competition, environmental disturbances

Scramble competition

predators capturing as many prey as quickly as possible.

- often happens in environment with abundant prey AND predator

- predators do not directly interact with one another

interference competition

competing predators interacting directly, typically leading to injuries or limited predatory success

- often happens in environment with limited prey availability

3 kinds of candy used

jolly ranchers, skittles, M&Ms

number of candy during the first round of predation

50

number of predators

6 to 7; 2 of each kind (fork, knife, spoon) initially

rules for predation

1. no scooping; must be horizontally picked up

2. prey must be placed into the paper cup (stomach)

3. stomach must be held upright

4. no usage of finger

how is learned avoidance simulated?

instructor will announce which prey is toxic during foraging session, and the predator must put its stomach content back to the grass mat.

stomach is simulated as;

paper cup represents;

predation must stop foraging when;

when stomach is full or time is up, predators should;

time of digestion is simulated by;

the period of tallying and calculating population size of prey type and predator proportions via excel sheet represents;

number of prey remaining

#initial - #eaten

number of prey at the beginning of next foraging session

#remaining + reproductive rate * #remaining

reproductive rate of toxic prey in the simulation

1.1

reproductive rate of other preys when one becomes toxic

2

carrying capacity of the prey

200

exercise terminates when;

stability is reached or 8 generations have been completed

to what value is the proportion of predators dependent on?

amount eaten by given predator divided by the amount eaten by all predators

Exercise 1

non toxic prey simulation: all prey with reproductive rate of 2, none of them becomes toxic.

Exercise 2

toxic prey simulation: toxic prey type announced during first foraging session. The predator that has eaten toxic prey must dump their stomach content, and must avoid the toxic prey. Reproductive rate of toxic prey is reduced to 1.1. Resistant predator will be specified in subsequent rounds, which will eat all 3 kinds of prey without restriction.

what happens to a predator during toxic prey simulation when it has a toxic prey inside their stomach starting from round 2?

their data will not be used, and their stomach content will be emptied to the mat.

graph for exercise 1

trend of prey population growth over time, and connect it to prey morphology.

- jolly ranchers went extinct

- skittles and m&ms showed similar trend & reached carrying capacity

graph for exercise 2

trend of predator population growth over time, and connect it to the toxicity and resistance

- forks went extinct

- knives and spoons competed

3 key to effective handling

1. not let the prey escape

2. efficiently subdue it

3. efficiently process (eat / digest / detoxify) it

if one altered the carrying capacity, the graph should be about

graph should be about prey count.

if one altered the toxicity, the graph should be about

graph can be about either of prey or predator

if one altered the predator count, the graph should be about

graph should be about the predator