Demographic PVAs Based on vital rates

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Demographic PVAs Based on vital rates
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Basic types of vital rates

• Fertility rates
• Survival rates
• State transition, or growth rates

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The estimation of Vital rates

• Accurate estimation of variance and correlation
  in the demographic rates
• We need to know
• The mean value for each vital rate
• The variability in each rate
• The covariance or correlation between each pair
  of rates

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Limitations of Matrix selection

• The assumption that the precise combinations of
  values that we observed the limited duration of a
  demographic study will always occur is unlikely
  to be correct.

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A more realistic approach

• Use the means, variances, and correlations
  between vital rates, and then simulate a broader
  range of possible values

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The problem of negative correlations

• A hypothetical individual is currently in size
  class 3 and has mean probability s30.95 of
  surviving for one year.
• If it survives it will either stay the same size,
  or grow to be in size class 4 with mean
  probability g4,30.10
• a33s3(1-g43)(0.95)(1-0.10) and
• a43s3g43(0.95)(0.10)

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The Desert Tortoise
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Size classes and definitions of matrix elements
for the desert tortoise assuming a prebreeding
census
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Estimated vital rates
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Pearson CorrelationsGrowth
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Pearson CorrelationsSurvival
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Pearson CorrelationsSurvival-Growth
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Key distributions for vital rates
0.5,0.001
0.5,0.2
0.5,0.01
The beta distribution
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Key distributions for vital rates
The beta distribution
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Lognormal
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Stretched Beta
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Matrix selection
Element selection
Vital rate selection