Taxonomic Reliability: Considered synonymous with M. mercadensis by cactus specialist Anderson (2001) and by the assessors. It is accepted as a species by cactus specialists Hunt (1999), provisionally, and Pilbeam (1999). The assessors have demonstrated that M. berkiana has no known characteristics that differentiate it from the surrounding M. jaliscana/M. mercadensis apart from the intensity of the flower color.

Justification:
This species is considered to be Vulnerable (under criterion D2) as it is known from only two locations, one of which was decimated by frost in the 1990's. Since that time a second population was discovered where an intact, small but abundant population remains. Therefore considering this new information the status has changed from Critically Endangered to Vulnerable. However, according to the assessors this species should be re-evaluated after its taxonomic status is confirmed. The species is provisionally assessed herein under the tentative placement of the taxa in M. berkiana

This species is known from two locations. It is endemic to the Mexican state of Jalisco, where it occurs in two subpopulations in the Sierra Huichol at elevations between 2,000 to 2,500 m asl. The species was originally described from north of San Andrés from two sites about 3 km apart, probably best considered a single location. A new location has been discovered (M. Cházaro pers. comm 2009).

This species is known from two locations, one where it is relatively common and another where it is extremely rare. In 1999 the species had a total population estimated to be less than 100 individuals, which referred to only a single location. Since that time a second population has been described and recent expeditions to the new location have found the species to be locally abundant within a very limited range.