The bacteria species has different strains. One strain produces a high level of a toxin; the other strain produces a low level of a toxin. Toxin production reduces the rate at which the bacteria can reproduce, reducing direct fitness. Humans acquire this bacteria in drinking water. When the group of bacteria has more of the toxin-producing strain, the bacteria are more likely to establish in the gut of the human, and cause disease. These groups reproduce rapidly, and do better than groups of bacteria with fewer of the toxin producing strain. Within a group, those bacteria that produce toxin have fewer offspring, but groups with more toxin producers leave more descendants, including toxin producers.
In this example, what process is most likely to maintain costly (altruistic) toxin production in these bacteria?
a. direct selection
b. indirect selection
c. inclusive fitness
d. group selection