Chapter 5: Stochasticity in Growth Rates Flashcards

1
Q

discrete (geometric) growth rate λ

A

the ratio of abundance in year t+1 (Nt+1) to abundance in year t (Nt)

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2
Q

λ =

A

Nt+1 / Nt

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3
Q

NT =

A

N0 * λ^T

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4
Q

continuous (exponential) growth rate

A

the instantaneous per capita growth rate

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5
Q

discrete (geometric) growth rate equations

A

λ = Nt+1 / Nt
NT = N0 * λ^T

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6
Q

r =

A

ln(λ)

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7
Q

λ =

A

e^r

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8
Q

continuous (exponential) growth rate equations

A

r = ln(λ)
λ = e^r

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9
Q

when use an exponential growth model for wild populations?

A
  • in newly established populations
  • populations recovering from catastrophic declines
  • invasive, pest outbreaks
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10
Q

population growth is often variable

A

stochastic

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11
Q

2 population growth variances

A
  • sample variance
  • process variance
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12
Q

which variance is visualized with error bars?

A

sample variance

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13
Q

what causes stochasticity in growth rate over time?

A
  • sample variance
  • process variance
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14
Q

stochasticity

A

variation or bounce

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15
Q

sample variance

A
  • aka observational error
  • nature isn’t varying, but our estimation error makes it seem like it is
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16
Q

process variance definition

A
  • the one actually affecting changes in abundance and the one we care about
17
Q

process variance: internal drivers

A
  • age structure
  • sex ratios
  • density dependence
  • connectivity
18
Q

process variance: changes due to interacting species

A
  • predation
  • competition
  • parasitism
  • human harvest
19
Q

process variance: stochastic factors

A
  • environmental stochasticity
  • demographic stochasticity
20
Q

process variance factors

A
  • internal drivers
  • changes due to interacting species
  • stochastic (random) factors
21
Q

environmental stochasticity

A

due to extrinsic factors that cause mean vital rates to change randomly over time

22
Q

example of an extrinsic factor

A

weather

23
Q

forms of environmental stochasticity

A
  • drought
  • early springs
  • warmer winters
  • summers
  • hurricanes
  • forest fires
24
Q

are the effects of environmental stochasticity more or less dependent on population size?

A

less

25
Q

what causes demographic stochasticity?

A

due to random deviations from mean birth and death rates

26
Q

demographic stochasticity population is made up of…

A

an integer number of individuals

27
Q

what size population is important in demographic stochasticity?

A

small populations

28
Q

does demographic stochasticity cause deviations?

A

yes, deviations from the 50:50 sex ratio

29
Q

how does demographic stochasticity arise?

A

arises strictly from population size and not from environmental variability

30
Q

demographic stochasticity causes…

A

unexpected declines in small populations

31
Q

how do you estimate exponential trends for wild populations?

A

regress log abundance sizes against time, the slope of the regression is r

32
Q

state space models to estimate growth rate can estimate:

A
  • population trend in the presence of both process and sample variance
  • how much of the total variance comes from each
33
Q

state space models to estimate growth rate is …

A

math and data heavy