Banana Slugs do well in moist and covered niches because the sun will not dry them up when they move, they are better hidden from aerial predators and they can blend in with the fallen leaves of similar color.
Fungi also does well in moist niches because it needs the water in order to grow.
Rabbits probably live in forests because they need brush and cover in order to hide from predators, and there is likely more food available for them to eat in the forest.
Beetles can be found in many places that include small dark places such as in tree bark, which is why a forest niche is suitable for them.
Redwood trees are what make up much of the Moist Evergreen Forest, and they probably like it because there is a lot of water available.
Butterflies might like to live in chapparal because there are a lot of shrubs, flowers, and bushes for them to land directly on top of (as opposed to a tall tree).
Gophers might live in chapparal because the land is much more dry than in a forest, which would probably help keep their tunnels more sturdy and less fragile.
Poison oak can be found in more than one niche, but it is in chapparal because an animal or person can easily walk through it without realizing what it is.
Lizards live in chapparal because the sun hits it more often than it would in a covered forest, giving them time to sun bathe.
I'm not sure about the different types of fungi and what type of niche they like to live in, but the one I observed was on a fallen tree, which I assume happens just as much in chapparal as it does in other niches.