Two species of lizard live on the same tree and consume the same sorts of food. regardless, neither species is in direct competition with the other. the key to this scenario is that one of the species is nocturnal; the other is diurnal. what is this called?

It is called 'resource partitioning'.

Explanation: The distinct nature of the two species allows them to co-exist in the same premise without any conflict. When one of the species (the diurnal) is out in search of food, the other prefers dwelling on the tree because of its nocturnal nature. Therefore, they are not confronted with each other as predators.

The food that is available at night is consumed by the nocturnal species and the food available during the daytime is eaten up by diurnal species. Hence, there is no competition.