Euploca is an almost cosmopolitan genus of flowering plants comprising approximately 168 accepted species, placed in the family Heliotropiaceae within the order Boraginales. The genus was first described by the American botanist Thomas Nuttall in 1837.
Under the broadly circumscribed Boraginaceae of the APG IV classification system (2016), Euploca falls within that large family; however, a concurrent revision of the order Boraginales published the same year recognises the smaller, segregate family Heliotropiaceae and places Euploca there. The genus was previously known under the names Hilgeria and Schleidenia, and its species were also accommodated in Heliotropium section Orthostachys. Molecular phylogenetic analyses established that these plants form an independent lineage more closely allied to the genus Myriopus than to Heliotropium, prompting their segregation into Euploca.
A distinctive physiological feature of the genus is its diversity of photosynthetic strategies: while many species employ the C4 photosynthetic pathway — characterised by a specialised leaf anatomy known as Kranz anatomy — the genus also contains C3–C4 intermediate species, making it of interest to researchers studying the evolution of carbon-fixation mechanisms in plants.
Etymology
The genus name Euploca was established by Thomas Nuttall in 1837. The name derives from the Greek eu- (well, good) and plokē (twining, braid), likely a reference to the plant's habit or inflorescence arrangement.
Distribution
Euploca has an almost cosmopolitan distribution, occurring across tropical and subtropical regions worldwide. The genus is particularly well represented in the New World, with species photographed as far as Bahia, Brazil.
Taxonomy Notes
Euploca occupies an unsettled position at the family level. APG IV (2016) embeds it within the broadly defined Boraginaceae, while a separate 2016 revision of Boraginales places it in the smaller family Heliotropiaceae. GBIF's backbone follows the Heliotropiaceae treatment (order Boraginales, class Magnoliopsida). The genus was formerly split across Hilgeria, Schleidenia, and Heliotropium sect. Orthostachys; molecular phylogenetics reunited these under Euploca and showed closer affinity to Myriopus than to Heliotropium.
