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Lecture 19

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


Department
Biology
Course Code
BIOL 3130
Professor
Andrew Mac Dougall
Lecture
19

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Bio 3130 lecture 19
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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