A new species of Russula, subgenus Compactae from California

A new species of Russula , subgenus Compactae , is described growing in association with coast live oak ( Quercus agrifolia ) in California. This species has previously been referred to locally as Russula subnigricans Hongo and Russula eccentrica Peck, but morphological and DNA evidence show that it is a distinct species which we call R. cantharellicola . Our analysis shows that there are multiple clades of what is called R. subnigricans , and that the California species clearly falls within one of those clades. As R. subnigricans has caused deaths in Japan, China, and Taiwan, the California species should be cautioned as potentially dangerous to those who consume it.