Indirect Effects - 19

Question 1

Define indirect effects

Answer 1

interactions between species that are propagated through one or more intermediary species

Question 2

What did Darwin speculate in terms of indirect effects

Answer 2

that cats positively affect flowers:
cats eat rats with eat bees and bees pollinate flowers so cats have a positive affect on flowers
(- x - x + = +)

Question 3

Define interaction chains

Answer 3

interaction chains link species that do not necessarily interact directly but by intermediary species that do interact

Question 4

What are the two types of interaction chains

Answer 4

density-mediated indirect effects
trait-mediated indirect effects

Question 5

Define density-mediated indirect effects

Answer 5

the series of direct effects that link the indirect interacting species are manifested as changes in density
most typically predator-prey relationships

Question 6

4 examples of density-mediated indirect effects

Answer 6

1. exploitation competition
2. trophic cascades
3. apparent competition
4. intransitive competition networks

Question 7

Define exploitation competition

Answer 7

when species share a common resource and exploiting the resource makes less for the competitor, negatively affecting the competitor

Question 8

Define trophic cascades

Answer 8

the addition or removal of top predators resulting in change

Question 9

Example of trophic cascades

Answer 9

the overharvesting of snail predators may be important factor for the massive die off of salt marshes

Question 10

Define keystone species

Answer 10

a species that has a disproportionally large impact on the diversity and stability of its community

Question 11

Example of keystone species

Answer 11

the removal of charonia effects echinoderms and reduce their population but without charonia, echinoderms would escalate and eat a ton of coral

Question 12

Define apparent competition

Answer 12

a reciprocally negative interaction that appears to be due to competition, but is actually due to a different mechanism. both serve as prey of a predator

Question 13

Define trait-mediate indirect effects

Answer 13

the series of direct effects that link the indirectly interacting species that are manifested as changes of species traits

Question 14

What are the 3 examples of trait-mediated indirect effects

Answer 14

1. behavioural shifts
2. morphological shifts
3. physiological shifts

Question 15

Example of behavioural shifts of trait-mediated indirect effects

Answer 15

when the change in property of some species causes a change in behaviour of a second species
ex. when larva are present, the small tadpoles go into hiding

Question 16

Example of morphological shifts of trait-mediated indirect affects

Question 17

Example of physiological shifts of trait-mediated indirect affects

Question 18

Explain density and trait-mediated indirect effects as being simultaneous

Answer 18

both types of indirect effects can happen at the same time and can interact. they can reinforce or oppose one another

Question 19

Explain how the stinkbug, hornworm, and nightshade can be an example of simultaneous indirect effects of trait and density-mediated

Answer 19

density = predator reduces density of herbivore (hornworm) which positively affects the plant (nightshade)
trait = herbivore feeds less to avoid predation which positively affects the plant
this is an example of a negative interaction between density and trait mediated indirect effects

Question 20

What significant interaction did Griffin and Thaler discover when both density and trait mediated indirect effects were simultaneously occuring

Answer 20

having both present did not further reduce the amount of damage compared with the amount of damage that was reduced by the density or trait effect alone

Question 21

Explain when trait effects appear to operate in the presence and absence of density effects

Answer 21

traits appear to operate in the absence but not in the presence of the density effects because there is a maximum amount that the herbivores reduce their feeding

Question 22

Why was the combined actions of trait and density mediated interactions greater than predicted based on the effects of each alone (2 possible reasons)

Answer 22

1. tadpoles may gain mass at a faster rate as they grow larger (snowball effect)
2. reduction in herbivory by small tadpoles may have non-linear effects on resources

Question 23

Define interaction modifications

Answer 23

occur when the presence of one species alters the outcome of an interaction between two other species

Question 24

Example of interaction modifications

Answer 24

macrophytes (algae/seaweed like) make it easier for northern pikes to blend in in the ocean and make it harder to be predated on