I grew up hunting in Illinois, and if I didn’t find them myself I wouldn’t believe it to be possible. Truth is that Los Angeles has been having steady rain for a few days and the weather is similar to spring in most morel areas. Also they are in my flower garden which I has a lot of different soils, mulch, and other medium that could have brought spores in from Other states. So possibly native, maybe not though. Found Jan 15, 2019