Dominant species in tundra

What are the dominant plant and animal species in the tundra biome?

I searched this up and I found the following:

Herbivorous mammals: lemmings, voles, caribou, arctic hares and squirrels. Carnivorous mammals: arctic foxes, wolves, and polar bears. Migratory birds: ravens, snow buntings, falcons, loons, sandpipers, terns, snow birds, and various species of gulls.

But which one is the dominant species predatorily and which one is the dominant species population-wise?