1. Population
A group of individuals of the same species that interact with each other in the same place at the same time
Metapopulation
A population of populations, linked
by genetic exchange (immigration and
emigration)

4. Describing a Population Distribution: total geographic range
including gaps
Density: number of individuals per area
Dispersion: how individuals are
dispersed

5. Fig. 9.8

6. Why Study a Population?
Explain distributions
Changes over time
Absences from suitable habitats

8. European Starling: 160
released in NY Central
Park in 1890

9. Zebra Mussel: larvae
released in ship ballast
in Great Lakes, 1988

10. Old growth piñon
Only juniper occurs in
the Gunnison Basin
today

11. How to study populations?
Select sample population and study growth
over time
Determine birth and death rates, average life
span, and other demographic variables

13. Demography: the vital statistics of a population
Reproduction
semelparous
iteroparous
nonoverlapping generations
overlapping generations

14. Usually, long-lived species are iteroparous
with overlapping generations
e.g., bear, humans, elephant
Short-lived species are more often semelparous
with nonoverlapping generations
e.g., insects, weeds
Exceptions include salmon, agave, bamboo
-- all are long-lived, but breed once and die
These categories are important to know when
trying to determine r for a species

15. Importance of Age Structure in a Population
Humans:
0-12 yr no births, r is –
r + and high
r + and low
r + and very low
r = 0 or -
The proportion of individuals in each age class
defines the age structure for the population

16. Age structure for three countries
Fig. 9.14
If r for each age class remains constant, the shape of the
diagram will not change. Then, it’s a stable age distribution.

19. r-selected r-selected r-selected K-selected K-selected K-selected
high r
short-lived
small size
short generation time
large litters, >1 per yr
unstable habitats
Type III survivorship
N variable below K
r-selected
high r
short-lived
small size
short generation time
large litters, >1 per yr
unstable habitats
Type III survivorship
N variable below K
r-selected
high r
short-lived
small size
short generation time
large litters, >1 per yr
unstable habitats
Type III survivorship
N variable below K
K-selected
low r
long-lived
large size
long generation time
small litters, 1 per year
stable habitats
Type I or II survivorship
N at or near K
K-selected
low r
long-lived
large size
long generation time
small litters, 1 per year
stable habitats
Type I or II survivorship
N at or near K
K-selected
low r
long-lived
large size
long generation time
small litters, 1 per year
stable habitats
Type I or II survivorship
N at or near K

20. Species with mixture of r and K-selected traits
Sturgeon
lives ~100 yrs
female produces 1 million eggs,
more eggs as it ages
Giant bamboo
lives ~250 yrs
flowers once, 1000s of seeds
Species with mixture of r and K-selected traits

21. Robert MacArthur
Hypothetico-deductive method in ecology
Competition and niche partitioning
r and K selection in life history strategy
Predator – prey theories
Optimal foraging
Island Biogeography
Population growth and dynamics
Generalist vs. specialist feeding
Paper on reserve: Fretwell, S The impact of Robert MacArthur on Ecology. Annual Review of Ecology and Systematics 6: 1-13.