Question About Ranking Up

I haven’t played this game for a hot minute, and have returned to it recently. But I’m not sure about this specific part of ranking up. Does this mean two different animal species for example fox and lynx? Or two different characters, in this case I could use my cheetah tree since it’s my highest?

I haven’t played this game for a hot minute, and have returned to it recently. But I’m not sure about this specific part of ranking up. Does this mean two different animal species for example fox and lynx? Or two different characters, in this case I could use my cheetah tree since it’s my highest?