Let’s consider the following experiments (based on a true project performed in Vermont in 1990’s, which aimed to study the social interaction and group selection).
We have two species of insects, A and B, who can live together but compete for resources. At the beginning of the experiment, we prepare 50 plastic jars, and put 100 individuals of A and 100 of B together in each jar. We give them food, water, and everything, and let them grow and reproduce. After one generation, both A and B have babies in each jar. We check all 50 jars, and select 5 jars, in which the numbers of A’s offspring are the highest among all 50. (Note: we do NOT care about the number of B’s babies in those jars. We only count A’s babies, and select the top 5). We then collect the babies of both A and B in these 5 jars.
Next, we randomly pick 5000 A’s babies and 5000 B’s from the collection of those top 5 jars (Note, in each jar, there are tens of thousands of A’s and B’s, but we only keep 5000 A’s and 5000 B’s babies, and discard the rest). We then randomly divide these 5000 A’s and 5000 B’s babies into 50 jars. This way, we will have 100 A’s offspring and 100 B’s offspring in each jar.
We give them food, water, and everything, and let the babies grow and reproduce. Then, we pick the top 5 jars, in which A has the most offspring. Again, we don’t care about the reproduction of B; we only count the number of A’s babies. And again, we get 5000 A’s babies and 5000 B’s (third generation) from these top 5 jars. And again, we evenly divide them into 50 jars, and start the fourth generation, and each jar again has 100 A’s and 100 B’s.
This repeats. In the real project, they let both species go for 16 generations.
After 16 generations, obviously, we would have selected the individuals of species A, which can reproduce very well with the presence of Species B. Let’s say, at beginning of the project, each A reproduces 30 babies on average (I made up the number). After 16 generations of selection, each A can reproduce 80 babies on average.
Now, we put 100 selected individuals of Species A (each of them can reproduce 80 babies on average) with 100 individuals of Species B that are newly caught from the field. I.e., these Bs and their ancestors did not grow in our jars, but in nature.
Question: what is your prediction on the reproductive success of Species A? Would it stay at 80 babies each adult, or would it go higher or lower? (4 pts), and what are your reasons? (6 pts).