You have been provided with some basic demographic data on a

You have been provided with some basic demographic data on a cohort of jumping mice in two prairie fragments in the upper Mid-West. In the Northern population, the site was burned several years ago and is now suffering encroachment from woody invasive plants. In the Southern population the site was recently burned and is relatively open with plenty of prairie grasses. Mice breed once a year and all individuals die by their fourth birthday. Females do not breed before their first birthday. Construct a life table of these data using the information below and calculate the net reproductive rate_, intrinsic rate of increaseand generation time for each population. How do these demographic parameters differ between the two populations? Can you speculate why?

North                           South      

Age       # alive       Av. # offspring   Age       # alive       Av. # offspring

0       500       0           0       100       0

1       200       1.2           1       90       3.4

2       120       1.9           2       80       5.0

3       30       1.6           3       50       1.2

4          0       0           4          0       0

Solution

Life table of North:

Life table of South:

Q. How do these demographic parameters differ between the two populations? Can you speculate why?

Mouse population in the North is bigger than in the South. The possible reason seems to be the fire in the south region, leading to the genetic drift in the population.

On the contrary, the reproductive rate is higher in the South as compared than that of the South population, which can be attributed to the lesser parent population as well as the lesser competition for the resources.

The South population exemplifies an expanding population, whereas the North population is a stable population.