Akodon spegazzinii is found in northwestern Argentina, in the provinces of Salta, Catamarca, Tucumán, La Rioja, and Mendoza, at altitudes of . Although its main distribution is in the northern provinces of Salta, Tucumán, and Catamarca, there are also scattered records from the more southern provinces of La Rioja and Mendoza, where it is likely restricted to patches of wet habitat. "Akodon alterus" has been reported from Jujuy, but this record was likely based on misidentified specimens of "A. boliviensis", and records of "Akodon spegazzinii" from Jujuy were based on misidentified "A. sylvanus". "Akodon spegazzinii" is known from a paleontological site in
Dicentra formosa on the western slope of the Sierra Nevada. Subsp. "oregana" grows in a small area of southern Oregon and northern California in serpentine soils in the Siskiyou Mountains. These subspecies are also distinguished by appearance: "Dicentra formosa" is widely grown as a garden plant, and several cultivars have been developed. Those marked have gained the Royal Horticultural Society's Award of Garden Merit: There are several hybrid cultivars involving "D. formosa", the eastern American species "D. eximia" and the Japanese species "D. peregrina": The Pacific bleeding-heart ("Dicentra formosa" subsp. "formosa") was first noted by Europeans when the Scottish surgeon and naturalist