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Population dynamics with Matrices. A is the population projection matrix.

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Presentation on theme: "Population dynamics with Matrices. A is the population projection matrix."— Presentation transcript:

1 Population dynamics with Matrices

2 A is the population projection matrix

3 Leslie 1945 summarized the existing theory at the time for populations with a certain age structure. Each age was one unit of time apart

4 F is the stage specific Fecundity. G is the survival from stage i to stage i+1

5 Lefkovitch (1965) proposed that the population stages need not have the same duration and that some in a given stage will survive and stay in the same stage after one year (or time interval).

6 In the above P 1, P 2, P 3, P 4 is the probability that females in stages 1-4 will remain in the same stage the following year.

7 Northern Spotted Owl

8 ROLAND H. LAMBERSON, ROBERT McKELVEY, BARRY R. NOON, CURTIS VOSS, A Dynamic Analysis of Northern Spotted Owl Viability in a Fragmented Forest Landscape*. Conservation Biology Volume 6, No. 4, December 1992 Or 133/chap8.pdfhttp://www.fs.fed.us/psw/publications/documents/gtr- 133/chap8.pdf

9 For the questions to follow we will assume a Lefkovitch population projection matrix structure as shown above

10 4 years of population data for the spotted owl is shown below. Using the 1991 to 1992 data what is the fecundity F of the pairs? (F2=0) Assume that P1=P2=0 i.e. Owls in stage 1 or 2 automatically advance to the next stage and that P3=0.94 i.e. 94% survival rate of mating pairs.

11 4 years of population data for the spotted owl is shown below. Using the 1991 to 1992 data what is the fecundity F of the pairs? (F2=0) F=F3=33/88=0.38 Assume that P1=P2=0 i.e. Owls in stage 1 or 2 automatically advance to the next stage and that P3=0.94 i.e. 94% survival rate of mating pairs.

12 4 years of population data for the spotted owl is shown below. Using the 1991 to 1992 data what is the value of G1? G1 is the fraction of stage 1 individuals advancing to stage 2. Assume that P1=P2=0 i.e. Owls in stage 1 or 2 automatically advance to the next stage and that P3=0.94 i.e. 94% survival rate of mating pairs.

13 4 years of population data for the spotted owl is shown below. Using the 1991 to 1992 data what is the value of G1? G1 is the fraction of stage 1 individuals advancing to stage 2. G1=7/36=0.19 Assume that P1=P2=0 i.e. Owls in stage 1 or 2 automatically advance to the next stage and that P3=0.94 i.e. 94% survival rate of mating pairs.

14 4 years of population data for the spotted owl is shown below. Using the 1991 to 1992 data what is the value of G2? G2 is the fraction of stage 2 individuals advancing to stage 3. Assume that P1=P2=0 i.e. Owls in stage 1 or 2 automatically advance to the next stage and that P3=0.94 i.e. 94% survival rate of mating pairs.

15 4 years of population data for the spotted owl is shown below. Using the 1991 to 1992 data what is the value of G2? G2 is the fraction of stage 2 individuals advancing to stage 3. G2=(87-88*.94)/9=0.48 Assume that P1=P2=0 i.e. Owls in stage 1 or 2 automatically advance to the next stage and that P3=0.94 i.e. 94% survival rate of mating pairs.

16 Four points are worth noting here about the eigenvalues, r for population projection matrices N t+1 =AN t : When r=1.0 the exponential term is a constant term, when r less than 1.0 the exponential term eventually goes to zero if r is greater than 1.0 will be exponential growth. If r is a complex number this corresponds to oscillations

17 Question Using a difference equation N t+1 =An t The dominant eigenvalue is =1.04. What is the implied population rate of increase? Will this population grow or get smaller?

18 Question Using a difference equation N t+1 =An t The dominant eigenvalue is =1.04. What is the implied population rate of increase? 4% increase each year

19 Question Using a flow equation The dominant eigenvalue is r=.02. What is the implied population rate of increase? Four points are worth noting here about the eigenvalues, r, for transport matrices In flow equations like above : When r=0 the exponential term is a constant term, when r is negative the exponential term eventually goes to zero if r is positive there will be exponential growth. If r is a complex number this corresponds to oscillations

20 Question Using a flow equation The dominant eigenvalue is r=.02. What is the implied population rate of increase? 2% increase each year

21 What is the transpose of the matrix below?

22

23 The population projection matrix and initial population are shown below. What is the population after 1 year?

24 The population projection matrix and initial population are shown below. What is the population after 1 year? Assume N 1 =AN 0

25 The last four years of a long population model simulation are shown below. What is the dominant eigenvalue for this population? And what is the percent growth rate?

26 The last for years of a long population model simulation are shown below. What is the dominant eigenvalue for this population? 1.11 And what is the percent growth rate? 11 %

27 Deborah T.Crouse, L.B. Crowder, and H. Caswell A stage-based population Model for Loggerhead Sea Turtles and implications for conservation. Ecology, 68 (5),


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