Final answer:
The most northern populations of wolves rely on caribou as one of their main prey species. The ecological selection that best fits this description is selective predation.
Step-by-step explanation:
The ecological selection that best fits the description is selective predation. The most northern populations of wolves rely on caribou as one of their main prey species. In this scenario, the wolves selectively prey on the slower caribou, while the faster caribou are more likely to survive and reproduce. This results in a population of faster caribou over time, demonstrating how predator-prey interactions can drive evolutionary responses and the adaptation of both predator and prey species.