Question

The biological species concept defines a species as a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring. This means that all members of these populations can contribute to a common gene pool. These populations belong to the same species. Genes are transferred between these populations through both direct and indirect gene flow.

Biologists used genetic techniques to look for gene flow in 12 wild populations of mice. The populations (designated A through L) were located along a 210-km transect line.

50 km A B C D

Some hints if you need them (hints open in new frame):

Hint 1: how to approach the problem

Hint 2: how to read this data grid

Hint 3: how to find species

The researchers found evidence of gene flow between some, but not all, pairs of populations. In the grid below, a "+" indicates a pair of populations in which direct gene flow was detected, and a "–" indicates a pair that showed no evidence of direct gene flow. For help reading this grid, see Hint 2.

The researchers discovered that the 12 populations could be organized into 3 distinct species. Populations A, B, and C each belong to a different species. Use the data in the grid to sort each population to the species to which it belongs.

Species 1 includes species A

Species 2 includes species B

Species 3 includes species C

Population D is species

      [ Choose ]            3 (which includes species C)            2 (which includes species B)            1 (which includes species A)      

Population E is species

      [ Choose ]            3 (which includes species C)            2 (which includes species B)            1 (which includes species A)      

Population F is species

      [ Choose ]            3 (which includes species C)            2 (which includes species B)            1 (which includes species A)      

Population G is species

      [ Choose ]            3 (which includes species C)            2 (which includes species B)            1 (which includes species A)      

Population H is species

      [ Choose ]            3 (which includes species C)            2 (which includes species B)            1 (which includes species A)      

Population I is species

      [ Choose ]            3 (which includes species C)            2 (which includes species B)            1 (which includes species A)      

Population J is species

      [ Choose ]            3 (which includes species C)            2 (which includes species B)            1 (which includes species A)      

Population K is species

      [ Choose ]            3 (which includes species C)            2 (which includes species B)            1 (which includes species A)      

Population L is species

Answer 1

We are going to assume population belong to the same species based on the gene flow, if gene flow is positively confirmed then the 2 populations in question belong to the same species. All of this is according to the biological species concept.

We already know species A, B and C are different species, now we have to group all other populations with these 3.

- Population D. This is species 2 (with population B)

- Population E. This one shows no gene flow with A, B or C, but it shows gene flow with F, which has gene flow with C. This is species 3

- Population F. This is species 3 (with C)

- Population G. This is species 1 (with A)

- Population H. This one shows no gene flow with A, B or C, but it shows gene flow with J, which has gene flow with E. This is species 3

- Population I. This one shows no gene flow with A, B or C, but it shows gene flow with L, which has gene flow with D. This is species 2

- Population J. This is species 3 (with C)

- Population K. This is species 1 (with A)

- Population L. This is species 2 (with B)

Species 1 has A, G, K

Species 2 has B, D, I, L

Species 3 has C, E, F, H, J