Indirect Effects - 19 Flashcards

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1
Q

Define indirect effects

A

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

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2
Q

What did Darwin speculate in terms of indirect effects

A

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 + = +)

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3
Q

Define interaction chains

A

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

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4
Q

What are the two types of interaction chains

A

density-mediated indirect effects
trait-mediated indirect effects

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5
Q

Define density-mediated indirect effects

A

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

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6
Q

4 examples of density-mediated indirect effects

A
  1. exploitation competition
  2. trophic cascades
  3. apparent competition
  4. intransitive competition networks
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7
Q

Define exploitation competition

A

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

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8
Q

Define trophic cascades

A

the addition or removal of top predators resulting in change

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9
Q

Example of trophic cascades

A

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

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10
Q

Define keystone species

A

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

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11
Q

Example of keystone species

A

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

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12
Q

Define apparent competition

A

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

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13
Q

Define trait-mediate indirect effects

A

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

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14
Q

What are the 3 examples of trait-mediated indirect effects

A
  1. behavioural shifts
  2. morphological shifts
  3. physiological shifts
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15
Q

Example of behavioural shifts of trait-mediated indirect effects

A

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

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16
Q

Example of morphological shifts of trait-mediated indirect affects

A
17
Q

Example of physiological shifts of trait-mediated indirect affects

A
18
Q

Explain density and trait-mediated indirect effects as being simultaneous

A

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

19
Q

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

A

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

20
Q

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

A

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

21
Q

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

A

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

22
Q

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

A
  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
23
Q

Define interaction modifications

A

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

24
Q

Example of interaction modifications

A

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