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Lecture 19

# BIOL 3130 Lecture Notes - Lecture 19: London Academy Of Music And Dramatic Art, Metapopulation, Population Viability Analysis

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PVAs

- Population Viability Analysis

- Doing a lot with a ittle-data limitations

- A little variation in reproduction success can have huge impacts on

population growth

- Not all life strastegies are equally important for population growth

- Putting it all together for conservation- managing for population growth with

limited data

Vital Rates

- Like most demographic analyses, PVAs focus on key birth and death

processes, acknowledging that not all have equal importance for population

growth

o Survival: typically refers to remaining in a stage class (age class)

o Growth: typically refers to going from one stage class to another

o Reproduction: typically refers to number of offspring per individual

(usually female)

Demography: what can be measured

- total population size: (Nt)

- Brood size: (Bt)

- Proportion of young (Pjt)

- Key issue: these data are relatively easy to collect

Variation in Population Growth

- If population growth lamda was the same every year, prediction of

population growth would be easy

- But Spatial variation among populations is also present

- Imagine a population where Nt+1= λtNt where λt=(0.86 with prob ½ [half the

females in the pop.], [1.16 with prob ½]-within a given year)

- Arithmetic mean of the 2 λ’s in 1.01 which would be the case for

deterministic (nonrandom) growth

- If you start with 100 individuals and the population grows for 500

generations then N500=N0(1.01)500=14,477=(100)(144.77)=14,477

- But population growth is subject to stochasticity [random variation]

- Now imagine same population (100 individuals growing for 500 generations)

but grow rate varies stochastically (randomly) either 1.16 or 0.86 among

years

- So with both growth rates about equally likely from one year to the next

(about 250 generations with ihgh or with low growth rates) then population

size after 500 is N500=N0[(1.16)250 x (0.86)250]=54.8

- Adding variation to population growth λ usually reduces population growth

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