I would like to inquire about online resources from I could download CNDDB (California Natural Diversity Database) data for the State of California. The CNDDB is basically a repository of California's rare species and natural community types (https://www.wildlife.ca.gov/Data/CNDDB/About). I was able to find certain online links to where you can view the data however there were no options available to download this data as point/polygon shapefile or a file geodatabase.
Detailed spatial data seems to require a CNDDB subscription.
You could put together quad level data (USGS 7.5 minute topographic quads) with this publicly available endpoint that lets you query what species are in a particular quad.
For example, for quad 3811957: https://apps.wildlife.ca.gov/bios/rest/Cnddb.ashx?o=cnddbQuickView&p=QuadSpecies&q=3811957&a=1