Poeciliidae
Fish in the genus Poeciliopsis, for example, have many different adaptations. Poeciliopsis monacha, P. lucida, and P. prolifica are part of the same group in that genus. However, they have three different ways of helping baby fish: P. monacha is lecithotrophic because it does not give its babies any resources after fertilization.  The mother fish swims around with her eggs in a sac but that is all. P. lucida shows a middle level of matrotrophy. This means that the eggs's metabolism can change the mother's metabolism, so some food chemicals go back and forth. P. prolifica is very matrotrophic.  The mother fish gives the eggs almost all of the food chemicals they need after fertilization. This level of matrotrophy allows Poeciliopsis to carry several groups of eggs that were start at different times.  This is called superfetation.