Applied Population Biology (class 17)

Question 1

Why are small populations demographically unstable?

Answer 1

Social interactions (especially those affecting mating) can be disrupted once population density falls below a certain level.

Question 2

What is the Allee effect?

Answer 2

The interaction between population size, population density, population growth rate and behaviour.
Eg: species that live in widely dispersed populations (bears, spiders and tigers) (slide 5 for graph)

Question 3

The smaller a population becomes, the more vulnerable it is to further:

Answer 3

1) demographic variation
2) environmental variation
3) genetic factors that tend to lead to lower reproduction

Question 4

What is Extinction Vortex and what effects it?

Answer 4

Tendency of small populations to spiral toward extinction because of all of these factors adding up:
1) demographic variation
2) environmental variation
3) genetic factors that tend to lead to lower
Each factor increases vulnerability to the other 2.

Question 5

What is Population Biology?

Answer 5

To manage rare or endangered species, to understand it’s ecology, natural history (distinctive characteristics), and status of populations including the dynamic processes that affect population size and distribution. Focuses on a single species.

Question 6

What are the types of natural history and population

biology important to conservation biology: (9)

Answer 6

1) Environment: habitat type, available habitat, variation, human impact
2) Distribution: range boundaries, is species clustered or distributed, migration routes
3) Biotic Interactions: food and other resources required, competition, predators, parasites. Other species required?
4) Morphology: Characteristics that allow a species to survive and distinguish it
5) Physiology: Food, water and minerals needed for survival, vulnerability to climate or weather change
6) Demography- trends in population size, age of reproduction
7) Behaviour- Actions of individuals mating, foraging, cooperative
8) Genetics: How much variation exists, adaptations
9) Interactions with HumansL harvesting, local knowledge, benefits vs harms.

Question 7

Methods for studying populations:

1) How to gather ecological Info?

Answer 7

• published literature
• unpublished “grey” literature
• field work - can sometimes upset long held expert opinion
• Ex: Exxon Valdez oil spill - lack of baseline data on population and species health

Question 8

Methods for studying populations:

2) Monitoring Populations
- Census

Answer 8

A count of the number of individuals
in a population. Works well for species that
aggregate (e.g., can census the full number of
seals on a particular rocky island). Can be
repeated to gain a trend over time if methods
are well documented.

Question 9

Methods for studying populations:

2) Monitoring Populations
- Surveys

Answer 9

Repeatable sampling method to
estimate the abundance or density of a
population or species. Can involve transects,
quadrats, plots, camera traps, direct
observation, listening for calls, observation of
signs (footprints, scat), mark-recapture.
-New methods: sound detection and eDNA in bodies of water

Question 10

Methods for studying populations:

2) Monitoring Populations
- Demographic Studies

Answer 10

Follow known
individuals of different ages and sizes in a
population to determine their rates of
growth, reproduction and survival. Allows for prediction of future growth.
Tagging or non-invasive studies (kangaroo faces)

Question 11

How can we contribute?

Answer 11

• Nestwatch
• frogwatch
• other counts
• local banding

Question 12

What is Population Viability Analysis? (PVA)

Answer 12

• extension of demographic analysis
• type of risk assessment: predicts the probability that a population or species will go extinct, change in size or change in area occupied

Question 13

How many years of data are needed to obtain a PVA with good predictive power?

Answer 13

10 years.

-Also need good estimates of population parameters and knowledge of ecology of species.

Question 14

Do Palm Cockatoos have long enough life spans to support their low reproductive success?

Answer 14

Used PVA to determine that populations are only viable with low mortality and that currently (with 40% of nestlings being harvested by humans) the population is NOT sustainable,

Question 15

What are Metapopulations?

Answer 15

• A population of populations
• shifting mosaic of populations which is linked by migration
• Common in ephemeral habitats

Question 16

What are source populations?

Answer 16

• Core populations

- Have fairly stable numbers and produce emigrants

Question 17

What are sink populations?

Answer 17

• Satellite populations

- Fluctuate in size with arrivals of immigrants. Population may decline without immigration from source populations

Question 18

What happens to sink populations in unfavourable years?

Answer 18

May go extinct. May be rescued or recolonized by migrants from source populations when conditions become faourable

Question 19

Metapopulation dynamics require biologist to take into account:

Answer 19

• founder effects
• genetic drift
• genetic flow

Question 20

What is rescue effect?

Answer 20

Even infrequent movement of individuals
between populations can restore much
of the lost genetic variation, rescuing a
small population headed toward
extinction.