Juniperus monticola compacta ≠ Juniperus zanonii
Plants of the World Online lists Juniperus monticola f. compacta Martínez and Juniperus compacta (Martínez) R.P.Adams as synonyms of Juniperus zanonii R.P.Adams. This is an obvious error which I explain below:
- Martínez described Juniperus monticola with three forms (compacta, monticola and orizabensis) as a subalpine to montane, dense-leaved juniper with small bluish cones and arched branches. J. m. compacta was described as a prostrate shrub that grows above the tree line on the volcanoes of the Trans-Mexican Volcanic Belt.
- Later, similar plants were discovered near the summit of Cerro El Potosí, in Nuevo León. These were assumed to be J. monticola f. compacta as well.
- In 2007, R.P.Adams et al. published their analysis of genomic data and the composition of the essential oils of what they had assumed was Juniperus monticola f. compacta from Cerro El Potosí. They found out that it differed quite a bit from J. m. f. monticola, but failed to compare it adequately with the J. m. f. compacta that Martínez had originally described. This led to the form being elevated to species rank as Juniperus compacta, encompassing the populations of the Trans-Mexican Volcanic Belt as well as from Cerro El Potosí and Sierra Mojada (Coahuila).
A few years later, R.P.Adams realized his misapplication error, retracted and began using the name J. monticola f. compacta sensu Martínez again, while separating the Nuevo León and Coahuila populations as J. zanonii.
A summary of how different authorities treat this complex and my proposal about how iNat should treat it is as follows:
The whole discussion leading up to this realization can be found here. I have since deleted the taxonomic swap where the discussion took place, as I had proposed a change that I now see is wrong.
