For clarification: "coevolution" in the real world refers to two or more species influencing each other's evolution, for example, in many predator-prey relationships in nature, the prey evolves traits that prevent it from being eaten, and in response, the predator will evolve traits to get around it. However, the adaptations often take hundreds or even thousands of years to become widespread, and Pokemon like Trubbish, which is said to be a mixture of domestic and industrial waste, may not be old enough as a species to have undergone many major changes in its biology.
We already know that some form of Darwinian evolution exists in the Pokémon universe exists thanks to Alola forms, and we know that it can be influenced by other Pokemon in the environment, as seen by Rattata becoming nocturnal to avoid its main predator, Yungoos.
I understood when writing this question that it may indeed be unanswerable, I was just wondering if there is any official information on the relationship between these Pokemon.
Also I'm a girl :P