Population Regulation

Question 1

Define the term “group selection” and describe the phenomena it was invented to explain

Answer 1

alleles can become prevalent in a population because they provide a benefit to the group, regardless of the effect the alleles bestow (or don’t) for the individual’s fitness

Question 2

Describe how cycles can affect population age structure

Answer 2

A particularly good recruitment year can have an enduring effect on the population’s age structure, eg. Lake Erie whitefish. A boom in population will be seen in that age group for years to come.

Variations in patterns of disturbance/stability, succession, and opportunity/constraints influence age structures of different species differently.

Question 3

Give an example to illustrate how climatic cycles may be linked to population cycles

Answer 3

Eg. Feral sheep on Hirta. 
High NAO index > mild wet winters in western Europe 
- Mean winter temperature on Hirta ~5°C
- Slow but continuous grass growth 
- Winter mortality is moderate > pop’n stays near K
Low index > cold winter 
- food supply collapses
- overcompensatory mortality

Question 4

Describe the characteristics of grouse population cycles and the factors that contribute to them

Answer 4

Grouse population cycles vary, some are cyclic, some are irregularly cyclic or non-cyclic. Grouse pop. is lowest when the parasite pop. is highest. The experiment clearly demonstrates that population crashes in Red Grouse are driven by the parasite and not “Group Selection”

Question 5

Describe how territoriality can result in density-dependent population regulation, with reference to its effects on reproduction and survival

Answer 5

Higher population size > more intraspecific competition for high quality territories >
Reduces per capita resources and increases time/energy in defense some individuals are forced to settle on territories in low quality habitat. Less food on poor territories will result in fewer young. Increased intraspecific competition is expected to reduce reproduction and survival.

Question 6

Describe the factors that determine territory quality

Answer 6

= the defense of a particular space and resource
Occurs when resources are limited (cm2 to hundreds of km2), can strongly influence population regulation and overwhelm other factors

A territory can be high quality because it contains:

• An abundance of food
• Good nesting site(s)
• Protection from predators

Question 7

Describe the evidence that territory quality is correlated with the fitness of the occupants of the territory

Answer 7

Dominant individuals defend high quality sites, eg. damselflys (Finke 1992). Larger males defend large holes, they then fertilize the eggs in those wholes, leading to larger males emerging from these high quality sites.

Question 8

Describe the circumstances under which hunting records can be used to reconstruct past population dynamics

Answer 8

When hunting is very common the amount of individuals harvested can approximate cycles