I dug one Arctostaphylos gland. We have moved native plants after they have been in for a year and the root ball from a gallon plant is normally 3 feet across and deep. It appears that many of our Ca. I believe these plants serve as energy shunts in an ecosystem. These plants act as bridges between water sources and dry hillside, different soil levels, different plant strategies and between different plant communities.
Starred items are most likely to have ecto.
They will sometimes change as the soil they are on changes or more often, as the community changes in maturity or composition. These species will out compete all other species in their environments. I believe if the research continues we will find many, many more species of Ca. Non-native plants that can also be Ecto. Arbutoid mycorrhiza is another type of mycorrhiza and only forms on some Arctostaphylos, the Arbutus and a few Rhododendron types.