It sounds like a fantasy novel, but the Red Queen hypothesis is about species competing and co-evolving with one another over long periods of time. It is named after the Red Queen in Through the Looking Glass, who said “it takes all the running you can do, to keep in the same place.” In other words, species have to constantly evolve and adapt, or they go extinct.
The Black Queen hypothesis is hard for me to understand, but it refers to
the queen of spades in the game Hearts, where the usual strategy is to avoid taking this card. Gene loss can provide a selective advantage by conserving an organism’s limiting resources, provided the gene’s function is dispensable. Many vital genetic functions are leaky, thereby unavoidably producing public goods that are available to the entire community. Such leaky functions are thus dispensable for individuals, provided they are not lost entirely from the community. The BQH predicts that the loss of a costly, leaky function is selectively favored at the individual level and will proceed until the production of public goods is just sufficient to support the equilibrium community; at that point, the benefit of any further loss would be offset by the cost. Evolution in accordance with the BQH thus generates “beneficiaries” of reduced genomic content that are dependent on leaky “helpers,” and it may explain the observed nonuniversality of prototrophy, stress resistance, and other cellular functions in the microbial world.
In other words, organisms can sort of help their rivals, and there can be some survival advantage to this over long periods of evolutionary time. I’m not sure I quite get it, but there it is.