Endotropis is a small genus of shrubs in the buckthorn family, Rhamnaceae (order Rosales), comprising around six accepted species native to western North America and northeastern/northwestern Mexico. The genus name was coined by Constantine Rafinesque in 1888 (Sylva Telluriana, p. 31), but for over a century its species were treated as part of the much larger, near-cosmopolitan genus Rhamnus. In 2016, a molecular phylogenetic study by Frank Hauenschild and colleagues (published in Taxon 65(4): 927) resolved this North American/Mexican clade as distinct from Old World and eastern North American Rhamnus, and resurrected Rafinesque's name Endotropis for it — recombining species such as Rhamnus crocea Nutt. and Rhamnus standleyana C.B.Wolf as Endotropis crocea and Endotropis standleyana. This split is reflected in the GBIF Backbone Taxonomy, though other references (including Plants of the World Online, and by extension English Wikipedia) continue to list the same species under Rhamnus.
As members of Rhamnaceae, Endotropis species share the broader buckthorn growth form: shrubs or small trees with simple, alternately arranged leaves whose veins curve upward toward the tip, a diagnostic character of the tribe. Flowers are small, yellowish-green, and typically unisexual on separate plants (dioecious), with four or five sepals and few or no petals. The fruit is a small, berry-like drupe containing two to four seeded stones, ripening dark. Endotropis crocea — known under its older name as the spiny redberry — is an evergreen shrub roughly 1–2 m tall found in chaparral habitats from California, Arizona, Nevada and Oregon south into northeastern and northwestern Mexico; its edible red berries were historically eaten by Native American communities. Endotropis standleyana, named for the botanist Paul Standley, is restricted to the Mexican states of Coahuila and Nuevo León.
Distribution
Species now placed in Endotropis occur in western North America and Mexico: E. crocea ranges across California, Arizona, Nevada and Oregon south through northeastern and northwestern Mexico and the Mexican Pacific Islands, typically in chaparral, while E. standleyana is known only from the Mexican states of Coahuila and Nuevo León.
Taxonomy Notes
Endotropis Raf. was published by Constantine Rafinesque in 1888 but went unused for over a century until Hauenschild (2016, Taxon 65(4): 927) resurrected it on molecular phylogenetic grounds, recombining a clade of western North American and Mexican species out of the polyphyletic genus Rhamnus (e.g. Rhamnus crocea → Endotropis crocea, Rhamnus standleyana → Endotropis standleyana). GBIF's Backbone Taxonomy accepts this segregate genus; Plants of the World Online (and hence English Wikipedia, which has no dedicated Endotropis article) still places these species in Rhamnus, so the two placements currently conflict.
Cultural Uses
The red, berry-like fruit of Endotropis crocea (as Rhamnus crocea) was eaten by Native American groups in the western United States; consumed in quantity it was reported to tint the skin red.
