As we saw last week, population size is important. Ideally, this means you started with a lot of genetically diverse founders, but of course that isn’t always the case. In the case of the Española Galapagos tortoises it was 12 females and 2 males. So, often you have to grow your population to stabilize it and
Population Growth
R and K Selection
R and K selection are concepts in ecology used to describe traits in the fluctuation of a population or population dynamics. For example, they describe the life-association traits between parent and offspring, such as quantity or number of young ones born at a time, quality of parental care, the age to maturity, and reproductive effort.
As we saw last week,
1- (1/2Ne)
Assume that the Española Galapagos tortoise captive population started with an Ne/N ratio of 0.7. Calculate their rate of loss of genetic diversity given their original population size of 14 tortoises (N=14). You will first need to solve for Ne, then plug Ne into the rate of loss of genetic diversity formula.
Now let’s work on growing the population. Generally, you will see growth rate represented in SSPs as lambda (λ). A λ of 1.08 denotes a population that is increasing at 8% a year, and likewise a λ of 0.92 denotes a population that is decreasing at 8% a year. Or, a λ >1 is always population growth and a λ < 1 is always population decline.
λ can be calculated by dividing the population size currently by what it was during the last generation. Or
λ = Nt/Nt-1
Now let’s think about the management implications of these values.
- If the Española Galapagos Tortoises have a
population growth rate of 1.02, what percent is the population increasing each year? What are the implications of this growth rate and what variables can impact this rate? - At a current population size of 43, what is a realistic target population size for 5 years in the future? How many offspring need to be produced each year to meet this target? Show your math.
- If each breeding pair produces an average of 8 offspring per year, how many breeding pairs do you need to meet your 5 year population target?
- What are the implications of variable breeding success rates in your captive breeding pairs?
Trending now
This is a popular solution!
Step by step
Solved in 3 steps
