Basic information: Scientists went out and
sampled individuals from the populations. Population size can be
very difficult to estimate, so scientists often assume all
populations are approximately the same size (as we are doing here).
When they directly sampled one of the populations, they found that
there are approximately 30 breeding females and 20 breeding males
(males have a higher mortality rate than females) in the
populations (remember that we are assuming that all populations
exhibit the same patterns). Also the scientists were able to use
capture/recapture methods to determine that the proportion of
migrants (migration rate: m) in any given population per
generation is 0.01. Scientists assume that migration is equal among
all the populations (this might be somewhat unrealistic since
migration might be more difficult among populations that are
separated a longer distance, but for the purposes of this
assignment we will assume all migration is equal). When they
actively looked at the difference in survival among the different
phenotypes they found that survival of the agouti phenotype was
approximately 63%. The survival of the black-backed phenotype was
approximately 62.8% and survival of the melanistic phenotype was
approximately 62.6%.

1. How genetically differentiated are the populations? (For
reference of comparison, a value of 0.3 or larger would be
considered very differentiated, a value close to 0 would be not
differentiated). (3 points)

2. What do these results suggest regarding gene flow among the
populations? Given only these results, do you suspect that
the alleles are fixed due to selection or drift? Why (this is just
a guess, but you must justify your answer) ? (2 points)

3. In order to follow up with the gene flow analysis, you decide
to directly measure selection on the fur color by using the
survival estimates relating fur coloration. What is selection on
the different phenotypes? Given this new information, and using a
quantitative explanation, is drift or selection responsible for
fixing the allele frequencies? (hint: you will need to use an
equation that relates selection and drift, and you will need to do
it for ALL 3 alleles) (3 points)

4. The melanistic phenotype has the lowest fitness of the 3
phenotypes, yet it still exists in relatively high proportion in
the various populations. Why? (1 point)

5. The Rio Negro tuco-tuco has both fragmented populations and
small population sizes. How do these interact to create issues for
allele fixation? Why might this be an issue for conservation
purposes? (1 point)