Humans

Humans, with their reputation of being especially adaptable, have come and gone from the city from time immemorial. Always finding a niche within Amaranth, it's only since the The Worldshock that humans have settle within the city proper (with few places elsewhere to go.)
Though not the most populous species of Amaranth by any means, their diversity and knack of getting into all walks of life gives other species the impression that they're literally everywhere. A great number of them are simply farmers, though.
Lastly, humans have somewhat of a reputation for.. gregariousness.. that has produced many hybrid species throughout the city..