Density dependence

Question 1

How can Inverse Density Dependence Occur in Small Populations?

Answer 1

SMall populations are prone to extinction.
Stochastic events may depress reproduction or increase mortality.
Inbreeding depression.
Allee effect describes a situations where there exists a correlation between population size/density and individual fitness within a population.

Question 2

How can Density-Independent Factors Influence Population Growth?

Answer 2

Temperature, precipitation, natural disasters (fire, flood, drought)
Exceeding organisms’ tolerance limits

Examples:

In white-tailed deer living in Minnesota, the average number of fawns produced decreases with the amount of snow.
The annual change in population is inversely related to the previous winter’s snow accumulation
- Direct (physiological) and Indirect (food availability)

Merriam’s Kangaroo Rat
Mojave Desert
Adapted to aridity
Reproduction is linked to seasonal rainfall
Production of annual plants

Question 3

What is a metapopulation?

Answer 3

models assume populations are large and occupy many habitats.
Rarely true in nature - fragmented habitats due to humans.
Levins = proposed that animals exist in subpopulations - metapopulation.
R<1 or R>1
Dispersal among populations preserve local extinctions.
Spatial ecology has developed as a result.

Question 4

what is landscape ecology?

Answer 4

geographic approach, habitat structure and patchiness.

Question 5

What is metapopulation biology?

Answer 5

relationship between patches, with-in patch dynamics.

Question 6

Examples of natural metapopulations?

Answer 6

Islands
Habitat islands = terrestrial or marine areas which are naturally isolated.
-lakes
-mountain tops
-unusual geology
-desert oases
-coral reefs
-estuaries

Anthropogenic metapopulation = remnant fragments after deforestation

Question 7

What, according to Hanski, defines a metapopulation?

Answer 7

• suitable habitat occurs in patches and may or may not be occupied by local breeding populations.
• even the largest subpopulation in the metapopulation has a risk of extinction = not many subsequent definitions consider a core population at low risk of extinction and satellite populations at a higher extinction risk.
• habitat patches are spaced in such a way as to permit recolonization after local extinction.
• dynamics of the local subpopulations are not synchronized.

Question 8

What is a Minimum Viable Population?

Answer 8

Number of individuals necessary to ensure long term survival of a species.

Question 9

What is Population Viability Analysis?

Answer 9

risk assessment that brings together species’ characteristics and environmental variability to forecast population dynamics and extinction risk

Question 10

What is Minimum Dynamic Area?

Answer 10

The area of suitable habitat necessary for maintaining the minimum viable population

Question 11

What is SPARC?

Answer 11

Spatial Planning for Area Conservation in Response to Climate Change

• 20 institutions
• Across the tropics
• Approx 200 000 Species (Verts and Plants)